NEW YORK - Serena Williams began her U.S. Open quarterfinal tentatively. Her shots lacked their usual sting, her attitude its usual conviction.
She was facing the last player she lost to at Flushing Meadows. She kept looking up at her coach, as if seeking solutions. After just 20 minutes Tuesday night, Williams was in danger of trailing by two service breaks. Not much later, the outcome was no longer in doubt, because the 23-time Grand Slam champion suddenly was in complete control.
Williams put aside some early shakiness and an early deficit, turning things around with an eight-game run en route to a 6-4, 6-3 victory over No. 8 seed Karolina Pliskova for a spot in the semifinals. It was Williams’ first win over a top-10 player this season.
“I was playing really not a good game,” said Williams, who was a point from trailing 4-1 and did fall behind 4-2 while making 22 of her 30 unforced errors in the first set. “I was thinking, ‘You know, I can play better.’ So that was the good news.”
Williams’ semifinal opponent will be No. 19 seed Anastasija Sevastova of Latvia, who surprisingly beat defending champion Sloane Stephens 6-2, 6-3 earlier Tuesday.
Sevastova, who retired in 2013 because of injuries and returned nearly two years later, advanced to her first Slam semifinal.
“Still long way to go, I think,” she said.
On the men’s side, Rafael Nadal began his quarterfinal as poorly as possible, shut out in a set by a 6-0 score for only the fourth time in 282 career Grand Slam matches.
On the previous three such occasions, he’d lost. On this one, he managed to come back to win, although it took 4 hours, 49 minutes for the defending champion and No. 1 seed to overcome his disastrous start and other stumbles along the way to beat No. 9 Dominic Thiem 0-6, 6-4, 7-5, 6-7 (4-7), 7-6 (7-5) for a semifinal berth at a third consecutive Grand Slam tournament, winning a physical, back-and-forth tussle that stretched across and concluded after 2 a.m.
When it ended, on an overhead by Thiem that sailed long, Nadal climbed over the net to hug his opponent.
“I’m very sorry for Dominic,” Nadal told a rowdy crowd in Arthur Ashe Stadium. “He’s a close friend on tour. He’s a great guy. A great player.”
On Friday, Nadal will face 2009 champion and No. 3 seed Juan Martin del Potro, who defeated No. 11 John Isner 6-7 (5-7), 6-3, 7-6 (7-4), 6-2.