No. 6 seed Elena Rybakina stormed to a 3-6, 6-1, 6-0 victory against No. 2 Iga Swiatek on Monday to move into first place in her group at the WTA Finals in Riyadh, Saudi Arabia.

Rybakina’s stunning rally, coupled with Amanda Anisimova’s victory against Madison Keys, guaranteed the Kazakh’s spot in the semifinals with a 2-0 record in the Serena Williams Group.

Anisimova will face Poland’s Swiatek for the group’s No. 2 spot in the semifinals after overtaking fellow American and No. 7 seed Madison Keys 4-6, 6-3, 6-2. Anisimova and Swiatek are both 1-1 in the round-robin competition.

Rybakina won 12 of the last 13 games to become just the second player this year to beat Swiatek after dropping the opening set. Keys did it at the Australian Open.

“She brings so much intensity to the court,” Rybakina said after the match. “I feel like she started the match really well and I was a little bit slow, so on serve straight away, she broke me. It was difficult to be down, but in the second set, I pushed myself.

“My serve improved, and I’m really happy that I stepped in and played better each point. I’m very happy with my performance.”

Rybakina had five aces and saved two of three break points in the one-hour, 37-minute match. She converted five of seven break chances against Swiatek.

“I’ve been playing really well the past few weeks,” said Rybakina, 26. “I was improving in each match, and the results were following after. Even here, I’m trying to focus on the little details, and it’s a great opportunity to play against the top players.”

Anisimova took advantage of 12 double faults by a rusty Keys in their one-hour, 43-minute match. Keys fell to 0-2 and was eliminated from the event, her first competition since sustaining an adductor injury at the U.S. Open.

Anisimova converted six of 10 break chances. She overcame a 3-1 deficit in the second set, then opened the third set with a service break and never looked back.

Anisimova and Swiatek have plenty of recent history together. Anisimova infamously lost 6-0, 6-0 to Swiatek in the Wimbledon final, but came back to defeat her in the U.S. Open quarterfinals 6-4, 6-3.

In the Stefanie Graf Group, No. 1 seed Aryna Sabalenka and No. 5 Jessica Pegula both won their opening matches on Sunday, defeating No. 8 Jasmine Paolini and No. 3 Coco Gauff, respectively.

–Field Level Media