NEW YORK (AP) -- In the heat of the moment, locked in a suddenly tight match after midnight at Flushing Meadows, Australian Open champion Stan Wawrinka snapped at a rowdy spectator, telling him to ''Shut up.''
An hour later, his 6-3, 6-4, 3-6, 7-6 (1) victory over 91st-ranked Thomaz Bellucci of Brazil in the second round of the U.S. Open complete, Wawrinka was able to laugh about the exchange.
''At the end of the day, they start to get a little bit drunk,'' Wawrinka said at his news conference, shaking his head and chuckling. ''It was OK. I had to talk to a few of them. At the end, it's normal. ... Everybody was into the match. That's OK. It can happen.''
In a match that began Wednesday and finished after 12:30 a.m. Thursday, the third-seeded Wawrinka quickly built a two-set lead before faltering a bit, muttering aloud at himself after one miss: ''Too many mistakes!''
By the time he was in the grind of the fourth set, Wawrinka was talking directly to a fan who was bothering him, turning toward the Arthur Ashe Stadium stands and saying: ''Shut up, man! Seriously, shut up.''
Once his mind was back on the tennis, Wawrinka was fine.
At the outset of the match, Wawrinka explained afterward, ''It was comfortable, because I was playing really good tennis. I think I was serving big. I was moving really well and taking the ball early, dictating every point. That's why it (looked) like - not easy, but it (looked) good for me.''
Bellucci, a left-hander, was ranked as high as 21st in 2010, but arrived in New York with a record of only 11-10 this season.
He entered Wednesday with a 5-19 record against opponents ranked in the top 10, including 0-9 on hard courts.
But after a poor start, he began giving Wawrinka some trouble.
Bellucci finally earned his first break point of the match in the fourth game of the third set. He converted the chance on a 10-stroke exchange, stumbling as he flubbed a shot that clipped a net cord, then righting himself to deliver a backhand lob winner that landed on the baseline for a 3-1 lead that helped him take that set.
Wawrinka called that ''one bad game.''
And then, making things really interesting, Bellucci went up a break at 2-1 in the fourth set.
But Wawrinka was able to break back to get back on serve. At 5-4 in the fourth set, Wawrinka held two match points, but Bellucci saved them to hold serve there and get to 5-all. With a chance to force a fifth set, though, Bellucci faltered in the tiebreaker.
''I tried to focus more on my game and not on what he was doing,'' Wawrinka said in an on-court interview. ''Tried to make him work a lot. I was playing a little bit smarter at the end of the match.''
Wawrinka made a real breakthrough at Flushing Meadows last year, eliminating defending champion Andy Murray and getting to his first major semifinal in the 35th Grand Slam tournament of his career.
He now has reached the third round of the U.S. Open for the fourth time in the past five years.
Wawrinka's next opponent is 92nd-ranked Blaz Kavcic of Slovenia, who eliminated 30th-seeded Jeremy Chardy of France 6-2, 6-7 (6), 6-3.
Follow Howard Fendrich on Twitter at https://twitter.com/HowardFendrich