HOUSTON -- Andy Roddick now will have just as many year-end No. 1 rankings as Andre Agassi does. And he can thank Agassi for a bit of help.

After a miserable 1½ sets Wednesday night, Agassi suddenly found his strokes and came back to stun second-ranked Juan Carlos Ferrero 2-6, 6-3, 6-4 at the Tennis Masters Cup. The result guarantees that the 21-year-old Roddick will become the second-youngest player to finish a season atop the ATP Tour computer rankings.

"I'm incredibly honored to finish the year as No. 1, but I'm probably more proud to be the sixth American ever,'' Roddick said.

"It's hard to reflect on what a year this has been, but I'm incredibly fortunate to be playing at home in the United States. To be able to share all of this with my friends and family is better than I could have ever imagined.''

Ferrero fell to 0-2 in the round-robin portion of the $3.65 million tournament and can't possibly qualify for the semifinals, which means the French Open champ won't accumulate enough points in the last event of 2003 to pass Roddick.

"To be No. 2 isn't bad,'' Ferrero said in Spanish. "I had a very good year. I'm very pleased with the whole year.''

Roddick, meanwhile, didn't have to set foot on court Wednesday. He won his first match of the tournament earlier in the week and plays Rainer Schuettler on Thursday.

Roddick finished last year at No. 10, and he's been dominant since hiring Brad Gilbert -- Agassi's former coach -- in June. With Gilbert, Roddick is 46-6 (.885 winning percentage), including a season-high 19-match winning streak. He beat Ferrero in the U.S. Open final in September, then replaced the Spaniard at No. 1 last week.

"It's an incredible accomplishment, especially the way he's done it, coming on late in the year. He has a lot to feel proud about,'' Agassi said.

"Glad I could help. I aim to please.''

He nearly didn't. Through 15 games, Agassi had 24 unforced errors to Ferrero's nine.

The turning point came with Ferrero serving in the fourth game of the second set, after Agassi slapped a forehand into the net to make it 30-love. Disgusted, he cracked his racket frame violently against his foot, drawing a warning from the chair umpire.

"I got frustrated,'' Agassi said. "I figured, worst-case scenario, I might pull out another racket, and it would feel better.''

While Agassi lost the next four points, he soon showed the skills that helped him win eight Grand Slam singles titles and finish 1999 ranked No. 1.

Both players held serve through the second set's seventh game, and then Agassi pounced. He hit a forehand winner down the line to get a break point, and a sizzling return led to Ferrero's errant backhand.

With a 5-3 edge in hand, Agassi pumped his fist, while most of the crowd (which included former President Bush) gave him a standing ovation.

When Agassi laced a backhand winner down the line to win the second set, he clearly was in control.

"It was like two different matches out there,'' Agassi said. "If you're second-guessing anything against Ferrero, he makes you pay the price for it. I never quite got settled until late in the second set.''

He got the only break of the third set for 2-1, ending it with another brilliant backhand down the line. From there it was just a matter of holding serve the rest of the way, and Agassi managed that, closing his comeback with a forehand winner.

In May, the 33-year-old Agassi became oldest man ranked No. 1. He has slipped to No. 5, in part because of his recent layoff, but he is the oldest player to qualify for the ATP Tour's season-closing event since Jimmy Connors was 35 in 1987.

Now Agassi helped Roddick join the elite group of 13 men who have ended a season on top since 1973.

And only Lleyton Hewitt -- who was 20 in 2001 -- was younger than Roddick.

As recently as 2000, Roddick was winning the U.S. Open junior title. He played just nine pro matches that year, finishing 158th in the rankings. He ended 2001 at 14th.

Roddick broke through this year, reaching his first career Grand Slam semifinal at the Australian Open, repeating that placing at Wimbledon, and then winning his first major at the U.S. Open. Capping 2003 by winning the Tennis Masters Cup would give Roddick a tour-high seven titles.

"Andy had No. 1 in his hands the whole week,'' Agassi said, "so regardless if I beat Ferrero or not, it was going to be up to him to solidify it.''