NEW YORK --
On the same day Andy Roddick announced this U.S. Open would be the last tournament of his career, fifth-seeded Jo-Wilfried Tsonga was upset by Martin Klizan of Slovakia in the second round.
The 52nd-ranked Klizan won 6-4, 1-6, 6-1, 6-3 on Thursday.
Before Tsonga's loss, top-five seeds on the men's and women's sides had played 14 matches at this year's tournament -- and won all 14 in straight sets.
Tsonga was the runner-up at the 2008 Australian Open and a semifinalist at Wimbledon this year. He had reached at least the third round in 18 straight Grand Slam trips, a streak that began in 2007.
"Today, I was not in a good shape," he said. "I didn't play good tennis. It seemed like I couldn't hit the ball enough hard to put my opponent out of position. I don't really know why it was like this today, but sometimes it happens with me."
The 23-year-old Klizan, meanwhile, had failed to make it past the second round in three previous Grand Slam appearances. He had never defeated an opponent ranked better than No. 49.
"I had no pressure," Klizan said. "If I lose, then I lose. I lose with (a) good player. But I won and I'm very happy. It means for me more that I beat finally a guy from top 10."
Added Tsonga: "I'm not a machine. Sometimes I'm tired, sometimes not. Sometimes in good shape, sometimes not."
Roddick's impending departure and Tsonga's loss were by far the biggest news of Day 4 at the year's last major tournament, overshadowing some otherwise noteworthy on-court developments in the afternoon.
There was a spate of victories by American men, two who are Roddick's contemporaries and good pals (32-year-old James Blake and 30-year-old Mardy Fish), and two who have been viewed as possible successors as the best the country has to offer in the sport (19-year-old Jack Sock and 24-year-old Sam Querrey).
"I saw the press conference just before I came out here. I had a feeling, thought it might be, because he's someone who puts heart and soul into every match. It gets tougher as you get older, and I don't think he could keep doing it the same way," said the 115th-ranked Blake, whose 6-1, 6-4, 6-2 upset of No. 24 Marcel Granollers of Spain was stunning for its ease.
No. 23-seeded Fish came back to beat two-time U.S. Open semifinalist Nikolay Davydenko 4-6, 6-7 (4), 6-2, 6-1, 6-2, the tournament-record 10th match in which a man erased a two-set deficit and came all the way back to win.
Men should be playing best-of-three-set matches at Grand Slam tournaments, the way women do.
"Why (do) girls play best-of-three sets and we should play best-of-five sets and have the same prize money?" Davydenko said, reviving a familiar debate.
"Why are we playing five-set matches? We need to play best of three in Grand Slams. Everybody will support (that idea, even Roger) Federer. For Federer, it's easy to win in one hour, two sets. No need to run (for) a third set."
Of course, for Federer, winning three sets before his opponent does never has been much of a problem, and the 17-time major champion moved into the third round with a routine 6-2, 6-3, 6-2 victory over 83rd-ranked Bjorn Phau of Germany on Thursday night.
This year's Open has generated plenty of drama in one area: comebacks from two sets down. When Fish rallied to beat Davydenko, it was the 10th time in this tournament a man has won after losing the first two sets -- already an Open record.
The 30-year-old Fish, seeded 23rd, missed two months this season because of an accelerated heartbeat but showed few signs of fatigue in playing nearly 3½ hours.
The only other time Fish won after trailing by two sets was against Victor Hanescu in the first round of the 2011 Australian Open.
Sock also reached the third round at a major tournament for the first time. He beat Flavio Cipolla 6-2, 6-2, 6-4.
Sock, ranked 248th, got in with a wild card. He saved 12 of the 13 break points he faced, while converting all six he earned on the 88th-ranked Cipolla's serve.
Sock teamed with Melanie Oudin of the U.S. to win the mixed doubles title at Flushing Meadows a year ago.
Information from The Associated Press was used in this report.