Simona Halep made the quarterfinals at the U.S. Open for the second straight year, beating Carla Suarez Navarro in straight sets.

The fifth-seeded Romanian won 6-2, 7-5 on Monday. She could face No. 1 Serena Williams next. The 22-time major champ plays Yaroslava Shvedova later in the day.

Suarez Navarro, seeded 11th, was seeking the sixth Grand Slam quarterfinal of her career.

Halep had a chance to serve out the match at 5-4 in the second set but got broken. She then broke Suarez Navarro's serve in the next game and successfully served it out in her second opportunity.

Later, Venus Williams went from down and out to a point from victory, then back again. In the end, she couldn't quite get past a woman a dozen years younger and never before at this stage of a Grand Slam tournament.

Williams failed to convert a match point and lost 4-6, 6-4, 7-6 (3) to 10th-seeded Karolina Pliskova of the Czech Republic in the fourth round of the U.S. Open on Monday, despite vociferous support from the Arthur Ashe Stadium crowd down the stretch.

"I really played the perfect point there," Williams said about her chance to end things while up 5-4, and Pliskova serving at 30-40, "and she managed to stay alive."

At 36, Williams would have been the oldest woman to reach the quarterfinals at any major since Martina Navratilova was 37 at Wimbledon in 1994.

Williams made it that far at Flushing Meadows a year ago, before losing to her younger sister Serena. This time, they had been on course for an all-in-the-family showdown in the semifinals; Serena's fourth-round match against Yaroslava Shvedova followed Venus' in Ashe.

Instead, though, Pliskova managed, just barely, to make it to her first Grand Slam quarterfinal at age 24. Until this tournament, she never had been past the third round in 17 appearances at majors.

"I was prepared that I'm going to play Venus — it's going to be tough, because all the people are cheering for her," said Pliskova, who leads the tour in aces in 2016 and produced eight in this match.

It took her a while to finish off this one, despite going up an early break in the third set and leading 4-2. Just as it seemed she would run away with it, Williams turned things around enough to go up 5-4 and hold a match point. But Pliskova erased that with a swinging forehand volley — the sort of shot Williams loves to hit — and followed it up with another aggressive forehand winner.

Then Pliskova broke to lead 6-5 and served for the match, getting three chances to close it at 40-love. After Pliskova frittered away one with a double-fault, Williams steeled herself and stepped up, smacking a volley winner, cross-court backhand winner and two forehand winners to break back for 6-all.

"To be honest," Pliskova said, "it was really difficult ... when I lost my serve."

Somehow, though, she pulled herself together enough to get through the tiebreaker as Williams faltered.

"In the 'breaker, I went for a little bit more," Williams said, "but I didn't put the ball in enough."

Now Pliskova will face No. 4 Agnieszka Radwanska or Ana Konjuh.