NEW YORK — Victoria Duval, a 17-year-old qualifier, stunned 2011 US Open champion Sam Stosur in the tournament’s first round Tuesday night, winning, 5-7, 6-4, 6-4.
‘‘A big moment, big stage. Not easy closing any match out, let alone a past US Open champion,’’ said Duval, who came in ranked 296th. ‘‘So happy I did it, though.’’
Duval jumped up and down with arms aloft after pounding a forehand winner to convert her fourth match point. And why not? Duval had never beaten a player ranked higher than 69th, never even faced one in the top 20, and was playing in just her second Grand Slam match. She also faced a former US Open champ, Kim Clijsters, in the first round at Flushing Meadows last year.
‘‘I know she didn’t play her best today, and this is the best I've played in my career, so I'm really excited,’’ Duval told the Louis Armstrong Stadium crowd. ‘‘I just tried to stay in the moment.’’
Duval was born in Miami, but lived in Haiti until she moved back to the United States at age 8. She trains in Bradenton, Fla.
The 11th-seeded Stosur, who had reached at least the quarterfinals in her last three trips to the US Open, was unhappy with the way she played. She made 10 double-faults and a total of 56 unforced errors, 21 more than Duval.
‘‘I'm not going to be a sore loser and say she didn’t do anything,’’ Stosur said. ‘‘But, you know, I think I certainly helped her out there today, that’s for sure.’’
Other seeded women joining Stosur on the way out were No. 17 Dominika Cibulkova, No. 20 Nadia Petrova, and No. 31 Klara Zakopalova.
Second-seeded Victoria Azarenka, the 2012 runner-up and a two-time Australian Open winner, needed 10 minutes and six break points to take the first game against 99th-ranked Dinah Pfizenmaier, then dominated the rest of the way in a 6-0, 6-0 victory.
‘‘There are things, you know, I feel like should be better,’’ Azarenka said. ‘‘But overall, it’s a good start.’’
Her 65-minute match in Arthur Ashe Stadium came after top-seeded Novak Djokovic began his bid for a second US Open title, and seventh major trophy, with nearly as swift and simple a result, beating 112th-ranked Ricardas Berankis of Lithuania, 6-1, 6-2, 6-2.
‘‘I played every point like it’s a match point,’’ said Djokovic.
After waiting since June for his next crack at a Grand Slam event, Monday’s rain forced Roger Federer to wait one more day. When he finally got going, Federer needed just 93 minutes to beat Grega Zemlja, 6-3, 6-2, 7-5.
Federer, who was bounced from Wimbledon in the second round, had 12 aces and 35 winners against the 62d-ranked Slovenian. The 17-time major champion is seeded seventh this year, his worst placement since 2002.
That didn’t really affect Tuesday’s opponent in Arthur Ashe Stadium. All that mattered to Zemlja, who owns fewer Grand Slam match wins, eight, than Federer owns Grand Slam titles, was that he was facing what he considered an impossible task.
‘‘If he’s the seventh seed or fourth seed or first seed, for me, that’s totally irrelevant,’’ Zemlja said. ‘‘He achieved so much. He’s the best player of all time. So I don’t think people can actually say something [negative] about the way he’s playing. You’re losing matches, you’re winning matches — that’s just tennis, and I'm sure he’s going to perform better than maybe he has done in the last few tournaments.’’
Federer entered Tuesday 32-11, a .744 winning percentage that doesn’t sound too bad, until you consider his career mark at the start of this season was .816, and he’s had years where he went 81-4 (.953) and 92-5 (.948).
‘‘Clearly, when you win everything, it’s fun. That doesn’t necessarily mean you love the game more. You just like winning, being on the front page, lifting trophies, doing comfortable press conferences. It’s nice. But that doesn’t mean you really, actually love it, love it,’’ said Federer, whose streak of 36 consecutive Grand Slam quarterfinals ended in June.
Jerzy Janowicz, who reached the semifinals at Wimbledon, was done in straight sets, too. But his US Open is over.
The 14th-seeded Pole felt as if a knife were stabbing him in his right side every time he tried to serve. After hurting his lower back Saturday, he lost, 6-4, 6-4, 6-2 to qualifier Maximo Gonzalez.
Ranked 247th, the 30-year-old Argentine hadn’t won a main draw match on the ATP Tour since April 2011.
‘‘I couldn’t jump,’’ Janowicz said. ‘‘I couldn’t make a service movement. It’s still better than yesterday.’’
Janowicz had a painkiller injection Monday, which allowed him to rotate so he could hit his backhand. But he described his serve during his match as ‘‘a push.’’ At one point in the third set, he even tried one underhand.