Linda Noskova has impressively secured her place in the WTA Finals semi-finals after a commanding victory over Coco Gauff, while Jessica Pegula's win against Marta Kostyuk has set up a thrilling decider for the remaining knockout stage spot.

Linda Noskova secured her place in the semi-finals of the WTA Finals with a 6-3, 6-3 victory over Coco Gauff on Tuesday, while Jessica Pegula knocked Marta Kostyuk out of the season-ending tournament with a straight-sets win.

The Czech, who beat Kostyuk in her opening match, has won both encounters without dropping a set and is assured of advancing to the knockout stage.

Gauff and Pegula are both 1-1, with the final round-robin matches on Thursday set to determine who joins Noskova in the last four.

Pegula's Dominant Performance

Pegula earlier bounced back from her opening defeat to Gauff with a 6-2 7-5 victory over Kostyuk, eliminating the Ukrainian from semi-final contention.

The American made a strong start, breaking Kostyuk in the opening game and taking another break to claim the first set. She carried that momentum into the second, breaking again at the start before the pair exchanged breaks twice.

Kostyuk's mistakes undermined her attempts to fight back, with the Ukrainian committing 17 unforced errors in the opening set compared with Pegula's three.

"Once I got off to a good start today, I definitely didn't want to give away that second set," Pegula said.

"In general I wouldn't want to, but I think it was a bit of an extra push to be able to give myself the best chance in this group, considering I did lose the first match."

Noskova's Path to the Semi-Finals

Noskova then took control against Gauff in a match marked by inconsistent serving from both players.

The pair traded breaks at the start of the first set, but Noskova broke twice more to take the opener. Gauff struggled to find consistency on serve again in the second set, allowing Noskova to build a 3-0 lead.

The American fought to stay in the contest but could not find a way back, as Noskova held her serve throughout the remainder of the set before sealing the win with an ace.

The result sends the Wimbledon champion into the semi-finals in her debut at the tournament, while Gauff will have another chance to qualify when she faces Kostyuk on Thursday.

Pegula takes on Noskova in the other final Group 1 match.

Kostyuk, who replaced world number one Elena Rybakina after the world number one withdrew with a viral illness, is making her first appearance at the WTA Finals.

"I saw that she's changing pace a lot, and I would struggle sometimes," Kostyuk said after her defeat to Pegula.

"Overall, I think I was pretty happy with my return today. You can obviously be better, everything can be better. Next time, maybe I'll be more ready."