NEW YORK — Venus Williams went from down and out to a point from victory then back. In the end, she couldn't 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 (7-3) to 10th-seeded Karolina Pliskova 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," the sixth-seeded Williams said about her chance to end things while up 5-4 in the third set, and Pliskova serving at 30-40, "and she managed to stay alive." Williams, 36, would have been the oldest woman to reach the quarterfinals at a major since Martina Navratilova was 37 at Wimbledon in 1994. Williams made it that far at Flushing Meadows a year ago before losing to younger sister Serena. This time, they had been on course for an all-in-the-family showdown in the semifinals; Serena followed Venus in Ashe and beat Yaroslava Shvedova 6-2, 6-3 in the fourth round for her 308th Grand Slam match victory, breaking a tie with Roger Federer for most in the Open era, which dates to 1968. Pliskova managed 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 and followed 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." She pulled herself together enough to get through the tiebreaker as Williams faltered. Now Pliskova will face No. 4 Agnieszka Radwanska or Ana Konjuh. Also reaching the quarterfinals Monday was 2014 French Open runner-up Simona Halep, who eliminated No. 11 Carla Suarez Navarro 6-2, 7-5. Now it's Halep's turn to try to deal with the serve of Serena Williams, who reached a tournament-best 126 mph, delivered 11 aces and won 28 of 30 first-serve points against Shvedova. In men's action, Juan Martin del Potro became the lowest-ranked man in the U.S. Open quarterfinals in 25 years, advancing when No. 8 seed Dominic Thiem stopped in the second set because of an injured right knee. Del Potro missed 2½ years' worth of major tournaments because of a trio of operations on his left wrist, so he's ranked only 142nd.Andy Murray eased into the quarterfinals for the 22nd time in his past 23 majors, beating No. 22 Grigor Dimitrov 6-1, 6-2, 6-2 at night. Murray now faces Kei Nishikori, who beat No. 21 Ivo Karlovic 6-3, 6-4, 7-6 (7-4).