Babe Ruth held the mark for decades, and Hank Aaron has held the career major-league home run record since before Alex Rodriguez was born. That doesn't mean the record is out of reach -- Ruth and Aaron have withstood many challengers, and they now must face more still. But just as Aaron's assault on Ruth's record came as a surprise, many have, for one unexpected reason or another, fallen short.

Here are 10 of the most intriguing contenders and pretenders to the throne:

Mark McGwire

	A bum knee kept Mark McGwire from reaching 600 home runs.

From 1997 to 1999, McGwire mashed 193 taters -- more than 64 per season. At that pace, McGwire, who turned 36 on Oct. 1, 1999, was on track to break Aaron's record before his 40th birthday. Alas, his right knee let him down. In November 2001, McGwire retired with only 61 more home runs than he had at the end of the '99 season, for a career total of 583, fifth best of all-time.

Big Mac hit home runs at a faster rate than anyone else in baseball history -- one per 10.6 at-bats. But he missed almost 600 games in his career, or enough at bats for almost 200 extra homers. What might have been? 770 homers, that's what might have been.

Jimmie Foxx
He was known as "The Beast" -- "He has muscles in his hair," said Yankees pitcher Lefty Gomez. And if 35 were the mandatory retirement age for ballplayers, Jimmie Foxx would be king. In 1942, when he turned 35, Double X had 527 homers, 11 more than Ruth at the same age and 17 more than Aaron. But battles with the bottle and injuries brought down the man sometimes called "the right-handed Babe Ruth," and he hit only seven homers after turning 35, for a total of 534.

Willie Mays

	Willie Mays is third all-time in home runs with 660.

According to one popular baseball myth, Giants outfielder Willie Mays would have the home run record ... if he hadn't had to play most of his career in San Francisco's Candlestick Park. But, in fact, Mays hit more dingers at home than on the road during his years at Candlestick, so that myth, like so many others, falls apart under examination. Still, Mays gave Ruth a good run, finishing his career in 1973 with 660 home runs, well ahead of Frank Robinson, who stands in fourth place with 586.

Josh Gibson
In the Baseball Hall of Fame, the plaque for Josh Gibson says he hit "almost 800" home runs. So why isn't he recognized as the major-league record holder? Maybe it's because he wasn't allowed into the major leagues -- Gibson was a Negro League catcher in the 1930s and '40s, "the black Babe Ruth."

Gibson became legendary for the length and the volume of his home runs, though we'll never know the exact number he hit because statistics for the Negro Leagues are unreliable. In 1947, three months before Jackie Robinson's debut with the Brooklyn Dodgers, Josh Gibson died of a stroke, at age 35. We don't know how many home runs Gibson would have hit in the majors -- in that sense, Ruth's and Aaron's gain is our loss.

Mickey Mantle

	Who knows how many homers Mickey Mantle would have had if he'd taken better care of himself.

New York Yankees center fielder Mickey Mantle was the perfect physical specimen, except for his feet of clay. He had 404 homers at age 30, but his hearty partying caught up with him, and he played only seven more seasons, his body a wreck. He retired after the 1968 season with 536 homers, most ever by a switch hitter.

Tony Conigliaro
The Conigliaro story is a sad one. At 22, he had 104 homers, the third-best total ever at that age. But on Aug. 18, 1967, the Boston outfielder was hit in the cheek by a pitch from Jack Hamilton, and he would never fully recover his eyesight. Then, in 1982, he suffered a debilitating heart attack, and he died eight years later, at age 45. Red Sox fans still wonder what Tony C. would have done had that fastball not found his face.

Mel Ott
In 1929, at age 20, New York Giants outfielder Mel Ott hit 42 home runs. When he turned 23, Ott had already hit 115 home runs, more than anyone else in history at the same age. But in his long career, Ott would never hit 42 homers again in a single season. Ott is best remembered for his distinctive hitting style, in which he lifted his right (front) foot and strode forward as the pitch approached, but he also holds the record for home runs in a single stadium -- he took full advantage of the short right-field dimensions of the Polo Grounds, knocking 325 homers out of that legendary park.

Sadaharu Oh
In his 22 years with the Yomiuri Giants, Japanese superstar Sadaharu Oh hit 868 homers, and he still holds the "world record" for career home runs. Oh passed Aaron's mark in 1977, and the two slight, mild-mannered sluggers have made many appearances together and have become friendly, still seeing each other often in Japan.

Oh's distinctive left-handed batting stance is what many remember about him. As Ott did, Oh held his right foot in the air as the pitcher threw, though Oh stood that way not for greater power but for greater balance -- his oddly steady stance reminded people of a dog peeing on a hydrant. His career and philosophy, including the origin of his stance, are chronicled in his remarkable autobiography, "A Zen Way of Baseball."

Bob Horner
In his first professional game, Atlanta Braves third baseman Bob Horner homered off Bert Blyleven, and he went on to win the 1979 NL Rookie of the Year award, despite the fact his smashing debut had come almost halfway through the season, on June 16. Horner kept up the rapid pace for a couple more years, and his perfect power stroke and bat speed led many to believe that he would challenge all the important home run records. But a series of injuries slowed down that quick bat, and he retired in 1988 with only 218 major-league homers.

Horner does carry three distinctions: in 1985, he tied a record with four home runs in a game (though the hapless Braves lost 11-8 to the Montreal Expos); in 1987, he became the first U.S. star still near his prime to play in Japan, for the Yakult Swallows, who gave him the number 55 in hopes he would hit 55 homers (he hit 31); and he remains one of the few major-leaguers who never played a day in the minor leagues.

Roy Hobbs
Those who have seen the lights-out hitting prowess of Roy Hobbs can only wonder what this pretender would have done had Harriet Bird not shot him in the stomach just as his career was getting under way. Also, of course, Hobbs had another handicap -- he's a figment of the imagination of Bernard Malamud, who further cast doubt on Hobbs' makeup by having him give in to pressure and strike out at the end of the novel "The Natural."

"Closer Look" will be a regular Page 2 feature, exploring a hot sports topic in greater detail.