Liudmila Samsonova Upsets Top Seed Marta Kostyuk in Guadalajara Open Quarterfinals

In an intense quarterfinal match on Thursday night at the Guadalajara Open presentado por Santander, Liudmila Samsonova staged a remarkable comeback to defeat top seed Marta Kostyuk. After losing the first set 4-6 and falling behind in the deciding set, Samsonova rallied to win 6-2, 7-5, securing her place in the semifinals.

Ranked No. 47 and seeded eighth in the tournament, this victory marks Samsonova's first semifinal appearance of the season and her first win against a top-10 player in 2026.

Kostyuk, ranked 11th, was considered the favorite and could have equaled Karolína Muchová's position in the WTA Race with a title win. She advanced to the quarterfinals after Taylor Townsend withdrew from their earlier match.

Earlier in the tournament, Samsonova defeated Kayla Day 7-6(4), 2-6, 7-6(5) and overcame Elsa Jacquemot 7-6(6), 6-2. Samsonova will next face the winner of the match between Peyton Stearns and wildcard Sloane Stephens.

In other quarterfinal results, Peyton Stearns defeated Sloane Stephens 7-6(6), 6-4, Cristina Bucsa, seeded sixth, won against Sara Bejlek 6-0, 6-4, and Isabella Jovic, seeded second, beat Magdalena Frech 6-2, 6-1. The semifinals have yet to be played.