Tom Tippett is the founder of Diamond Mind Baseball, a highly-realistic strategy-oriented computer baseball game. He is also the designer of the simulation used in ESPN Classic Fantasy Baseball. This article originally appeared on the Diamond Mind web site. Click on their site for more baseball articles.

Speed. What's it really worth?

A couple of weeks ago, a member of SABR (the Society for American Baseball Research) pointed out that the most popular methods for evaluating offensive production -- such as Bill James' Runs Created, Pete Palmer's Batting Runs and Stolen Base Runs, on-base plus slugging (OPS) -- fail to take into account all of the ways that a player can use his speed to gain bases and runs. Here's an excerpt from his initial post:

"There are many subtle benefits of speed, such as the team at bat getting into less double plays when a fast player is on first, more errors made by the defensive team when compensating for speed, and more fastballs seen by upcoming batters when a base stealer is on base. In Seattle, we see these situations play themselves out on a frequent basis with Ichiro as a leadoff batter.

There is one aspect of speed that is very basic and fundamental, but to the best of my knowledge is not reported in current statistical player rating systems. This component would be when a runner goes from either first to second on a single, or first to third on a single ...

If an Ichiro, for example, advances a 100 extra bases over the course of a season over a slower runner or, say, 50 bases over the average runner, this is a significant, tangible and profound difference. How you calculate the value is something I am unsure of, but there is no question it is of value ..."

I decided to take a crack at measuring those unmeasured aspects of speed. My approach doesn't qualify as a rigorous scientific study of the question, but by examining Ichiro's 2001 season in great detail, I believe we can come up with a reasonable estimate.

There may be others with as much or more raw speed -- Tom Goodwin comes to mind -- but Ichiro's combination of speed, smarts, and hitting skill is unique among today's players. So I think it's fair to say that Ichiro is able to use his speed to greater advantage than any other player in the game today.

Speed is already being measured in many ways
Before we start looking for unmeasured aspects of speed, let's quickly go over the elements that are already being measured fully.

		Fri., June 7 I don't think Ichiro batting third is a permanent move. Once Edgar Martinez returns to the lineup, I expect Ichiro to return to the leadoff spot. What precipitated the move is that for the first time in a couple of years the Mariners were having trouble scoring runs. The plus for Ichiro in the three-spot is that he's batting better than .500 with runners in scoring position. But that's where stats can be deceiving, because some of those hits are infield hits with a runner on second that don't drive in the run. But Mariners manager Lou Piniella must have figured it was worth trying this new lineup heading into interleague play to see if the Mariners can manufacture some runs -- probably as a stopgap until Edgar returns. Of course, Piniella didn't have to tinker with his lineup last year as Seattle amassed an AL-record 116 wins. But each year presents its own challenges, and Edgar's injury is one of them. Boston is experiencing a similar situation in Manny Ramirez's absence. When a hitter of that magnitude is missing from your lineup, you're going to feel it sooner or later.

Every time Ichiro beats out a bunt or a grounder for an infield hit, his batting average goes up. Every time a grounder sneaks through for a single because the infielders were playing a step or two closer than normal, that too shows up in his batting average. Every time he stretches a single into a double or a double into a triple, his slugging average goes up. And there's nothing hidden about the value of his stolen bases, either; they are included in the official statistics and the Runs Created formula.

How else does speed enter into the equation? Using play-by-play data for the 2001 season (licensed from STATS, Inc.), we took a look at Ichiro's ability to pressure the defense into making errors, his ability to take extra bases on various types of batted balls, and a few of the ways his presence affected his teammates.

Forcing errors as a hitter
Of the 3,357 errors committed by major-league fielders last year, 1,928 allowed a hitter to reach base. There were 136,861 plate appearances in which the batter put the ball in play, so the average batter reached via error 1.4 percent of the time.

Ichiro put the ball in play 647 times last year, so an average reach-on-error count would be 647 x .014 = 9. But Ichiro actually reached via error 12 times. That could just be luck, of course, but since we're trying to put an upper limit on the impact of speed, let's be generous and assume that his speed was responsible for all three of those extra times on base.

Overall, 81 percent of last year's errors put the batter on first, 17 percent put the batter on second, 1 percent put the batter on third, .05 percent saw the runner score on the play, and 0.7 percent resulted in the batter being put out trying to get an extra base on the error. Ichiro wound up on first 10 times (83 percent) and on second twice (17 percent), so he didn't get any extra bases on his errors than did the average batter.

Forcing miscues as a basestealer
Another common source of errors is the stolen base where the catcher throws the ball into center field. Ichiro stole 56 bases last year, forcing six throwing errors in the process. How does that compare with other runners?

In 2001, runners were credited with 3,103 stolen bases. But some of those came on double steals, and there were only 2,970 plays on which one or more steals were credited. On those 2,970 plays, someone (most often the catcher) threw the ball away 190 times, or 6.4 percent of the time. So a reasonable expectation is that someone stealing 56 bases would force 56 x .064 = 4 throwing errors. Ichiro forced six, so we could say that he gets credit for two extra bases.

But that would understate his contribution, because it compares him not to the average player, but to the average basestealer. The vast majority of players didn't induce a single catcher throwing error all season. So it's more accurate to give Ichiro credit for five to six extra bases here. We'll call it six.

He also forced one balk, but that's only fractionally higher than you'd expect given the number of times he was on base.

And he induced three pitchers to throw the ball away on pickoff attempts. That's two more than the norm. He was also picked off once, which is normal for someone who was on base as often as he was.

Distracting the pitcher
What about his ability to disrupt the pitcher? The Mariners drew walks at the same rate with Ichiro on base as they did overall. They struck out 10 fewer times than you would expect, suggesting that hitters may have been getting better pitches to hit. But 10 extra balls in play would normally yield only about three extra hits, and we don't really know whether any extra hits were actually produced.

As a group, the club's No. 2 hitters were no better in that spot than in the other batting order positions in which they appeared. Bret Boone was essentially the same hitter whether he was in the No. 3, No. 4 or No. 5 slot, so it's hard to say that having Ichiro on base made a difference for him. Neither was there any evidence that subsequent hitters got behind in the count while waiting for Ichiro to steal, thereby hurting their own ability to perform at the plate.

Without more precise tools to measure the potential impact of a runner on subsequent hitters, we can't say with certainty that Ichiro had no impact. But neither can we say that he did, either for better or worse.

Advancing on hits
Each year, to help us assign baserunning and throwing ratings for our computer game, we analyze each runner's ability to take extra bases on hits and each outfielder's ability to prevent these advances.

We begin by computing overall averages for different situations -- going from first to third on singles, second to home on singles, and first to home on doubles. Our analysis focuses on lead runners, ignoring anyone who would score automatically on these plays (such as a runner who trots home from third on a single). It ignores hits where no runner could be expected to advance, mainly infield singles and ground-rule doubles. And it makes various adjustments for the effects of playing on natural grass and artificial turf (it's harder to advance on a groundball single on turf), the location of the batted ball (it's much easier to go first to third on a single to right than a single to left, and harder to advance on balls hit directly at the outfielder than on balls hit in the gaps or down the lines), and the number of outs (runners are more aggressive and more successful with two outs, and they take fewer chances trying to score with nobody out).

After compiling the overall averages, we track how often each runner advanced, held, or was thrown out in each of these situations, and we credit runners for any extra bases they take compared with the averages. Adding up the net bases taken across all of these situations gives us an overall measure of the advancement rate for each runner.

The most surprising thing about this type of analysis is the relatively small number of baserunning opportunities we end up with. Players only reach base so many times in a season, and after you subtract the times when (a) the inning ends without any more hits, (b) they can jog home on a double, triple or home run, and (c) they are blocked by another runner, players rarely get more than 50 opportunities per season to take an extra base on a hit.

Last year, Ichiro had 45 such opportunities, and he took six more bases than the average runner. He wasn't once thrown out trying in those situations. Six extra bases may not seem like a lot, but it was enough to qualify for our top baserunning rating.

(That's not to say Ichiro was the best baserunner in the game last year. There were others who qualified for our top rating, with Brian Jordan, David Eckstein, and Tony Womack ranking as the leaders of that elite group.)

Advancing on flyballs and groundballs
Our baserunning program doesn't attempt to rate players for their ability to advance on flyballs and groundballs, mainly because our research in that area suggests that the skill of the runner is much less important than the direction and distance of the batted ball.

With a runner on third and less than two out, for example, the runner scores on about 81 percent of all flyballs. When the success rate is high even for average runners, we don't get a lot of help in distinguishing the talented runners from the not-so-good, and to date, we have chosen to leave these plays out of our analysis of baserunning skill.

But we won't leave that out for this article. Instead, we'll review of all of Ichiro's times on base from the 2001 season, and that should give you a good feel for his ability (or inability, as the case may be) to advance on groundballs and flyballs.

Ichiro on third base
Speed isn't much of a factor when a runner is on third base. Any hit scores him automatically, and because there are a lot of situations where it takes two outs to work the runner over to third in the first place, the often ends before the runner can do much of anything except dance down the line a few times.

In 2001, Ichiro was on third base for 146 events, where an event is usually a plate appearance by a subsequent hitter but could also include intermediate actions such as wild pitches and stolen bases. Of those 146 events, the majority didn't test his speed in any way:

36 batters walked, struck out, or were hit by a pitch
27 other hitters made the third out of the inning
30 scored the runner on a base hit of some kind
4 batters popped up to an infielder

That's a total of 97 events where speed wasn't a factor, leaving another 49 where speed might enter into the equation.

On the 14 flyballs with less than two out, Ichiro scored 10 times on sacrifice flies, held third three times, and scored one more time when the flyball was dropped for an error. As I pointed out earlier, the vast majority of runners score from third on flyballs anyway, so there's no evidence here that Ichiro's speed was a factor. He scored on all the deep flyballs, and on the five medium or shallow ones, he scored twice and held third three times.

On the 25 groundballs with less than two out, Ichiro scored an impressive 20 times, though four came on infield errors, one on a second-to-first double play, and five more on force outs at second. Even though Ichiro may not have been the focal point on these plays, and even though other runners were put out, 20 of 25 is a high rate for scoring on infield grounders. Based on a quick review of the typical advance rates in these situations, we'll credit him with seven extra bases.

The most interesting aspect of Ichiro's time on third was the threat of the double steal. On ten occasions, another runner stole second while Ichiro was perched on third, and the trailing runner was safe at second every time. Nine of those 10 steals went to two runners (Mark McLemore seven, Mike Cameron two) who could have stolen those bags on their own, but the threat of Ichiro breaking for home may have been enough to turn an 85 percent chance into a sure thing. (The play-by-play data don't tell us whether the catcher threw down to second or just held the ball to keep Ichiro where he was.) Interestingly, Ichiro held third every time, so his impact, if any, would show up only in the stats of his teammates.

Based on league averages, you'd expect a runner who was on third for 146 events to score twice (total) on passed balls or wild pitches. Ichiro scored once on a wild pitch, so there's no direct evidence that his speed paid off in this area.

Ichiro on second base
Compared with third base, speed is more of a factor with a runner on second, but the number of opportunities to use it is still lower than you might think.

In 2001, Ichiro was on second for 230 events, but more than half can be ruled out right away. The batter failed to get the ball in play 64 times, made the third out 42 times, drove him in with an extra-base hit 21 times, and either lined out or popped up to an infielder five times. Of the remaining 98 events, 26 were singles that have already been taken into account in our baserunning analysis, so there were 77 events that might demonstrate speed in ways that we have not already considered.

Ichiro stole third 14 times and was caught twice. On six of the steals and both of the caught stealings, a trailing runner moved up to second base, so we can give Ichiro credit for eight extra bases here.

There was nothing unusual about Ichiro's ability to advance on groundballs. With one exception, he advanced when the ball was hit behind him and stayed at second when the ball was hit in front of him. The exception was a groundball to short on which he took third anyway, so if we want to be generous, we can give him credit for one extra base.

Twenty-eight flyballs were hit with Ichiro on second and less than two out. On four of them, he was blocked by a runner who held third on the play. He held second on 14 of the remaining 24 flyballs, and quite a few of them were hit to the deeper parts of the ballpark. He took third nine times, eight of which were on balls hit deep enough to advance even the slowest runners. And he was doubled off second once. All in all, this is an unimpressive record that falls 2-3 bases short of the overall averages.

On wild pitches and passed balls, Ichiro moved up a base three times, two fewer times than we'd expect based on the overall averages.

Ichiro on first base
Last season, there were 305 events with Ichiro on first base, though he often didn't hang around very long. Fully 51 of those events involved an Ichiro steal attempt, but because those are already part of the statistical record, we'll skip them here.

Of the remaining 254 events, the batter failed to put the ball in play 68 times, made the third out in some other way 42 times, drove Ichiro home with a triple or homer 11 times, and either lined out or popped up to an infielder seven times. Subtract those events, along with the 53 singles and doubles that we've already considered in our baserunning analysis, and we're left with 73 events to look at.

Note: Astute readers will notice that we just ruled out 53 singles and doubles because our baserunning analysis covered them. But a few paragraphs back we wrote that Ichiro only had 45 qualifying baserunning opportunities. That's because quite a few of the 53 singles and doubles were of the types we exclude -- infield hits, ground-rule doubles, and plays where someone else was the lead runner -- from our running analysis.

Thirty groundballs were hit with Ichiro on first, and ten of them resulted in a second-to-first double play. That's a 33.3 percent rate, which is very close to the overall average of 34.2 percent, so there's no evidence that Ichiro was able to break up many double plays. He was also forced at second six times. When he did move up to second, it was generally on the types of groundballs that force the infielder to make the play at first no matter who's on base.

Ichiro held first on 21 of 23 flyballs. The other two resulted in plays at the plate, and Ichiro took second on the throw one time and was thrown out at second once. All in all, this is a slightly below-average performance.

While on first, Ichiro took second on a wild pitch or passed ball six times, which is par for the course.

Summing up
Let's see if we can pull all this together. The goal was to identify the ways in which Ichiro's speed leads to increased scoring in ways that are not already reflected in his official stats or in metrics like Runs Created.

By looking at Ichiro's 2001 season in detail, we found the following:

3 more times reaching on error than the average hitter
6 more errors on steal attempts than the average
2 more errors forced on pickoff throws
6 extra bases taken on singles and doubles
7 extra bases on grounders while at third base
1 extra stolen base for a teammate while at third base
8 trailing runners advanced on double steals
1 extra base on a grounder while at second base
-2 fewer bases taken on flyballs while at second base
-2 fewer bases taken on WP/PB while at second base

That's a total of 30 extra bases compared to the average runner. Depending on the base and the number of outs, advancing one base can be worth anywhere from a tenth of a run to half a run. So, without trying to put a value on each individual base gained, we can say that Ichiro probably created 6-12 extra runs with his speed in ways that are not already measured.

By the way, it's tempting to say that this figure must be higher. After all, we're giving him credit for seven extra bases on groundballs while he was on third. And two of the six catcher throwing errors were on steals of third, with Ichiro scoring on both. So that's nine runs before counting the other bases on this list, right? Well, not quite. In some of those nine innings, Ichiro would have scored on a subsequent hit anyway.

Coming back to the original question, we can reasonably conclude that Ichiro's speed does matter in ways that don't show up in the official stats, but the impact isn't as high as the 50 bases that was suggested.

The main reason is that runners have fewer unmeasured opportunities to deploy their speed than we might think. The threat of taking an extra base may always be there, but the batter makes that threat irrelevant at least half the time by walking, striking out, popping up, ending the inning with a flyout or groundout, or driving the runner home with a long hit.

One more thing
A couple of astute SABR members pointed out that very fast players may already be getting a little extra credit in metrics like Runs Created, Batting Runs, and OPS.

Suppose Ichiro lines a ball into the gap, where it's cut off by the right fielder, but not before Ichiro can use his speed to stretch that single into a double. The better offensive metrics would give Ichiro credit for a typical double, meaning that he gets credit for (a) not making an out, (b) advancing himself to second base, and (c) advancing other runners by the number of bases typically taken on a double, which is often two but sometimes three.

When Ichiro legs out a borderline double, however, it's always a two-base advance for the other runners, meaning that his doubles aren't worth quite as much as the average. The same is true of an infield single -- Ichiro gets full credit for a single, but an infield single almost never scores a runner from second, while many other singles do.

The bottom line
All things considered, offensive metrics like Runs Created probably do understate Ichiro's value by a few runs. (OPS, on the other hand, doesn't include steals at all, so it can understate the value of someone like Ichiro by a larger amount.)

That's good to know, but there doesn't appear to be any evidence to suggest that those measures are dramatically understating Ichiro's value, or that of any other speedster, as an offensive player.