The man who could be the best US men's tennis player of his generation is now retired: Andy Roddick lost in the fourth round of the US Open today against Argentina's Juan Martin del Porto, 6-7 (1), 7-6 (4), 6-2, 6-4, reports AP. "For the first time in my career, I'm not sure what to say," an emotional Roddick told the crowd after the match, reports USA Today. "I appreciate your support along the way. I know I haven't made it easy for you at times." Roddick surprised the tennis world last week by announcing—on his 30th birthday—that he was calling it quits after the tournament. He remains the last American male to win a Grand Slam event, in 2003. Click for a tribute to his career.