NEW YORK — Wimbledon semifinalist Jerzy Janowicz was upset by a qualifier in straight sets in the first round of the US Open Tuesday.
The 14th-seeded Pole took an injury timeout for a trainer to massage his back, threw a racket, and argued with the chair umpire during his 6-4, 6-4, 6-2 loss to 247th-ranked Maximo Gonzalez.
Gonzalez, a 30-year-old Argentine, had lost five straight Grand Slam first-round matches.
Janowicz had never been past the third round at a major tournament before his run at Wimbledon, which ended with a loss to eventual champion Andy Murray.
The combustible 22-year-old fell in the first round at Flushing Meadows last year in his only previous appearance in the US Open. He had 11 double faults and 53 unforced errors Tuesday.
On the women’s side, sixth-seeded Caroline Wozniacki held off qualifier Duan Ying-Ying to win her first-round match. With boyfriend Rory McIlroy in the stands, Wozniacki fought off a set point in the second to win, 6-2, 7-5.
The 133d-ranked Duan had a chance to serve out the set at 5-3 in her Grand Slam debut. But the 2009 US Open finalist broke back. Then Duan had a set point on Wozniacki’s serve that she couldn’t convert.
Wozniacki broke serve in the next game, then staved off three break points to clinch the win.
Seventh-seeded Petra Kvitova weathered another tough first-round match at the US Open, needing three sets and nearly two hours to beat 92d-ranked Misaki Doi.
Kvitova won, 6-2, 3-6, 6-1, on a windy day at Arthur Ashe Stadium.
‘‘I like big matches on the big stadium, but the people — it’s too much crowds for myself, I think,’’ she said.
Kvitova has reached at least the semifinals at the other three major events, but she has never made it past the fourth round at Flushing Meadows.
She’s also struggled in the North American swing leading up to the US Open, but she made a breakthrough last year. Kvitova won two of those tournaments and reached the semifinals at another in 2012, then matched her longest run at the year’s last Grand Slam tournament.
‘‘So I have good motivation to improve my results here,’’ she said.
The final set Tuesday was closer than the score in this rare matchup of two lefties. After Kvitova went up a break at 2-0, Doi had a chance to break right back but couldn’t convert.
Two years ago, Kvitova became the first reigning Wimbledon women’s champion to lose her first US Open match in the same season. She was in danger of another early exit Tuesday when she made 15 unforced errors in the second set.
But she’s hardly fazed by three-set matches. Kvitova recently played six straight across three tournaments, winning four of them.
Doi, from Japan, fell to 0-4 against top 10 opponents.
No. 10-seeded Roberta Vinci, a quarterfinalist at Flushing Meadows last year, beat Timea Babos, 6-4, 6-2. She’s reached a career-high ranking this summer at age 30 after making the Round of 16 at the French Open and Wimbledon.
No. 13-seeded Ana Ivanovic and 14th-seeded Maria Kirilenko got off to quick starts, each winning in under an hour. Ivanovic, the 2008 French Open champ, beat Anna Tatishvili, 6-2, 6-0. Kirilenko won, 6-1, 6-1, against Yanina Wickmayer, a semifinalist at Flushing Meadows four years ago whose ranking has fallen to 57th.
Christina McHale, a 21-year-old from Englewood Cliffs, N.J., snapped a five-match losing streak by beating 45th-ranked Julia Goerges, 6-4, 6-3. McHale’s ranking had fallen to 114th.
On the men’s side, Milos Raonic won his first Grand Slam match while seeded in the top 10. The 22-year-old Canadian defeated qualifier Thomas Fabbiano of Italy, 6-3, 7-6 (6), 6-3.