Instead of continuing a slow fade from the peak of men's tennis to the outskirts of the top 20, Andy Roddick has decided to step away from the sport.

Roddick, 30, announced at a press conference Thursday he will retire after the U.S. Open, meaning a man who has been the face of U.S. men's tennis since Pete Sampras and Andre Agassi retired could be passing the torch as soon as this week. The first chance for Roddick to extend his farewell tour will come Friday when he meets talented 19-year-old Australian Bernard Tomic in the second round of the U.S. Open.

"On some big moments this year, I think I've known I was done," Roddick said. "Walking off at Wimbledon, I felt like I knew. Playing here, I don't know what it was, but I couldn't imagine myself being here in another year.

"Whatever my faults were, I've always felt like I've never done anything halfway. This is probably the first time in my career that I can sit here and say, I'm not sure I can put everything into it physically and emotionally. I don't know if I want to disrespect the game by coasting home."

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Roddick has been the best American men's player for much of the past decade, reaching No. 1 in the world for the first time in Nov. 2003 and amassing 32 ATP World Tour titles and 33 Davis Cup victories. His lone grand slam title came at the 2003 U.S. Open, but he reached the finals of Wimbledon three times, falling to Roger Federer each time including a 16-14 fifth-set heart breaker in 2009.

The departure of Roddick will again shine a light on the dearth of young American tennis talent capable of filling the void.

Hard-serving 27-year-old John Isner cracked the top 10 for the first time this year, but his 2011 quarterfinals appearance at the U.S. Open is the only time he has made it to the final eight of a grand slam. Veteran Mardy Fish, 30, reached No. 7 in the world last August, but injuries and signs of age have sent him tumbling to No. 25 a year later. And promising 24-year-old Sam Querrey has bounced back from an injury-plagued 2011 season to reenter the top 30, but he still has yet to prove he can consistently reach the second week of a grand slam.

What Roddick's legacy in the sport will be depends whether his career is viewed in comparison to some of the other greats of his era or on its own merit.

On the one hand, he used his powerful serve and potent forehand to remain a decade-long fixture in the top 10 and keep the U.S. relevant in men's tennis. On the other hand, he never could unequivocally say he was the best in his sport, always overshadowed by Roger Federer in his prime and eclipsed by the likes of Rafael Nadal, Novak Djokovic and Andy Murray in recent years.

Injuries and age have caught up with Roddick this year more than any other, sapping the power in his trademark serve and forcing him to rely on gradually declining groundstrokes. He lost in the third round or sooner of all three prior grand slams and has slid to No. 22 in the ATP rankings.

[Related: Andre Agassi says Andy Roddick was victim of great era]

Asked why he'd announce his retirement now rather than waiting until after his final match, Roddick said he wanted the chance to say goodbye on his terms.

"I don't know how tomorrow is going to go," Roddick said. "I hope it goes well and I hope I'm sticking around, but I just imagine coming off the court tomorrow to an empty locker room. I think I want a chance to say goodbye and also if I do run into some emotions tomorrow or four days from now or however long, I don't want people to think I'm a little unstable."

Perhaps the most telling sign the end was near for Roddick came Tuesday after his workmanlike straight-sets first-round win at the U.S. Open over fellow American Rhyne Williams.

When a TV reporter noted that Roddick's 31st birthday was on Friday and asked what he'd like as a present, Roddick didn't say he wanted a second U.S. Open championship like he might have a few years ago. Instead he chuckled and said he was just hoping to reach the second week.

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