NEW YORK (AP) The Latest on the US Open (all times local):
Kristina Mladenovic, who had never been past the third round at a major before this week, is into the quarterfinals at the U.S. Open.
The 40th-ranked Frenchwoman beat Ekaterina Makarova 7-6 (2), 4-6, 6-1 in a match that didn't end until past midnight Monday morning. The 13th-seeded Makarova made the semifinals at Flushing Meadows a year ago, but Mladenovic, 22, was the more poised player in this one, twice rallying from down a break in the first set. She won with style too, pulling off a between-the-legs shot on the way to taking a point during the second set.
In their previous two meetings, Mladenovic won the first set only for Makarova to beat her in three. There was no repeat this time, with Mladenovic bursting to a 4-0 lead in the final set.
Mladenovic next faces 43rd-ranked Roberta Vinci, who advanced without playing a point when 25th-seeded Eugene Bouchard withdrew from their fourth-round match Sunday after sustaining a concussion when she slipped and fell in the locker room Friday.
No. 1 Novak Djokovic is into his 26th straight major quarterfinal after a hard-fought victory over Roberto Bautista Agut at the U.S. Open.
Djokovic dropped a set for the first time this tournament, and the 23rd-seeded Spaniard made him work throughout the 6-3, 4-6, 6-4, 6-3 win Sunday night.
Bautista Agut, who has never reached a Grand Slam quarterfinal, was down a break in the second set. But he won the last four games to pull even, running down every shot, ripping big forehands and leaving Djokovic to stomp on his racket in disgust.
The nine-time major champ responded by raising his level to close out the match in four sets. He next faces 18th-seeded Feliciano Lopez.
Feliciano Lopez has reached the U.S. Open quarterfinals for the first time at age 33, with Fabio Fognini unable to recreate the magic from his upset of Rafael Nadal.
The 18th-seeded Lopez beat Fognini 6-3, 7-6 (5), 6-1 on Sunday. He'll next face the winner of the night match between Novak Djokovic and Roberto Bautista Agut.
Fognini, seeded 32nd, had rallied from down two sets and a break to stun Nadal in a match that didn't end until early Saturday morning. The shots that were hitting the line against Nadal were landing out Sunday, with 40 unforced errors to 28 winners.
Fognini called for the trainer to adjust his back and neck during and after the second set, and he also needed an inhaler in the third.
Lopez is in a Grand Slam quarterfinal for the first time since 2011.
Serena Williams is three wins away from completing the first Grand Slam since 1988 after a crisp straight-set victory over young American Madison Keys.
The 21-time major champion had been getting off to slow starts recently but was focused from the beginning Sunday, winning 6-3, 6-3 in just 68 minutes in the fourth round.
She faces sister Venus in the quarterfinals.
The 20-year-old Keys nearly matched Williams booming serve for booming serve but made just enough mistakes. She had 19 unforced errors to just six for Williams, including six double-faults - most of them coming at inopportune times, including match point.
Eugenie Bouchard has withdrawn from her fourth-round match at the U.S. Open because of a concussion.
The 25th-seeded Canadian was scheduled to face Roberta Vinci on Sunday. She slipped and fell in the U.S. Open locker room Friday.
On Saturday, she withdrew from two doubles matches but was still hoping to play singles. Tournament officials announced Sunday that she had a concussion and would not play.
Serena Williams has taken the first set against young American Madison Keys in their highly anticipated U.S. Open fourth-round matchup.
The 21-time major champion won the set 6-3 on Sunday as she seeks to complete the first Grand Slam since Steffi Graf in 1988.
Williams has been plagued by slow starts recently but was crisp from the beginning in this one. The 20-year-old Keys looked unintimidated, though, as the two traded booming serves.
That is, until the 19th-seeded Keys suddenly double-faulted twice in a row while serving at 3-4 to hand over a break. Williams promptly served out the set.
With a win, she would face sister Venus in the quarterfinals.
A furry invader briefly interrupted a third-round women's doubles match Sunday at the U.S. Open.
In the third game between Casey Dellacqua and Yaroslava Shvedova and Jelena Jankovic and Aleksandra Krunic, a squirrel scurried onto the court. Laughing, the players tried to shoo it away, but the visitor couldn't seem to find the exit.
A ball girl finally chased the squirrel into the stands. Dellacqua and Shvedova, who are seeded fourth, went on to win 2-6, 7-5, 7-5.
Venus Williams cruised into her first U.S. Open quarterfinal since 2010.
The seven-time major champion routed 152nd-ranked qualifier Anett Kontaveit 6-2, 6-1 in 50 minutes Sunday to set up a potential meeting with her sister. Serena Williams faced fellow American Madison Keys next at Arthur Ashe Stadium.
The 19-year-old Kontaveit had played just two Grand Slam matches before this tournament, losing both, and was making her U.S. Open debut. She upset 31st-seeded Anastasia Pavlyuchenkova in the second round.
Kontaveit was clearly overmatched by the 35-year-old Williams. The Estonian had 21 unforced errors, including four double-faults.
Jo-Wilfried Tsonga has quietly rolled through the U.S. Open.
The 19th-seeded Frenchman has yet to drop a set or lose his serve through four rounds. He beat countryman Benoit Paire 6-4, 6-3, 6-4 in 1 hour, 42 minutes Sunday to set up a quarterfinal meeting with defending champ Marin Cilic.
Tsonga, the 2008 Australian Open runner-up and a former top-five player, missed the first 11 weeks of this season because of an arm injury. He had lost three of his last four matches coming into the U.S. Open but has served extremely well this week, facing just two break points overall and none Sunday. He's also had a favorable draw and has yet to play a seeded opponent.
That will change against the ninth-ranked Cilic as Tsonga seeks to reach the semifinals at Flushing Meadows for the first time. It's the only major where he has never made it to the semis.
Tsonga is 12-1 in his career against fellow Frenchmen in Grand Slam matches. The 41st-ranked Paire was playing in the fourth round at a major for the first time. He upset fourth-seeded Kei Nishikori, last year's runner-up, in the first round.
Defending champion Marin Cilic overcame a tweaked right ankle thanks in large part to 23 aces and returned to the U.S. Open quarterfinals with a 6-3, 2-6, 7-6 (2), 6-1 victory over 27th-seeded Jeremy Chardy of France.
Cilic smacked serves at up to 132 mph, relying on that big shot to carry him in the pivotal third-set tiebreaker. Cilic hit four serves in that tiebreaker and each one was an ace.
The ninth-seeded Croatian has won his past 11 matches at Flushing Meadows, where he reached his first Grand Slam final a year ago.
He rolled his ankle early in the second set but seemed to be moving fine by late in the third, which he ended with a down-the-line backhand passing winner on the run.