For Serena Williams, history will have to wait.

Williams’ quest for an Open era record 23rd major title was stopped dead in its tracks by Karolina Pliskova, who defeated Williams, 6-2, 7-6 (7-5) in the U.S. Open semifinals on Thursday night.

Pliskova, who defeated Venus Williams earlier in the tournament, became only the third woman to beat both Williams sisters at the U.S. Open.

“I always know I have a chance to beat anyone if I’m playing my game,” Pliskova said after the match. “This is something amazing and I’m really excited to be in the final, especially to beat a player like this — Serena is a champion, so it’s never easy to play her.”

Pliskova came out on a mission, dominating the first set to win, 6-2, in just 26 minutes.

The 24-year-old from the Czech Republic is the WTA leader in aces, and her serve was dialed in on Thursday, and Williams looked off from the beginning of the match.

Williams put up a valiant effort in the second set, but Pliskova continued to answer every time it looked like Williams was going to seize momentum.

The match ended in the most unlikely of ways — a double fault by Williams.

Williams, 34, was playing on back-to-back days, having won a challenging three-set match against Simona Halep in the quarterfinals on Wednesday night, so fatigue could have been a factor against Pliskova’s power game.

Williams was looking to become the first woman in the Open era to win 23 Grand Slam singles titles. She’s currently tied with Steffi Graf at the top of the list.

With the loss Williams will also lose her world No. 1 ranking for the first time in 186 weeks. The streak tied her with Graf for the longest ever. Angelique Kerber will be the new No. 1 no matter her result in her semifinal match against Caroline Wozniacki on Thursday night.

Earlier in the tournament, Williams won her 308th Grand Slam singles match, passing Roger Federer for the Open era record.

Despite battling a shoulder injury, Williams took home her seventh Wimbledon singles title in July to tie Graf’s career Grand Slam record. She’s coming off a third-round loss at the 2016 Rio Olympics, and entered the U.S. Open having played only three matches since Wimbledon.

Pliskova advances to her first major final on Saturday, when she will play the winner of Kerber and Wozniacki.

Source: CBS Sports / U.S. Open results: Serena Williams upset in semifinals by Karolina Pliskova