Marta Kostyuk reacts after winning her quarterfinal match in the French Open Tuesday in Paris. (AP photo)

PARIS (AP) — Marta Kostyuk, the best player on clay this season and a vocal supporter of Ukraine amid the war with Russia, will play her first major semifinal at the French Open against a Russian.

Kostyuk won an intense all-Ukraine quarterfinal against Elina Svitolina 6-3, 2-6, 6-2 on Tuesday. That set up Kostyuk against Russian teenager Mirra Andreeva, who thumped Romanian veteran Sorana Cirstea 6-0, 6-3.

In men’s play, 20-year-old Jakub Mensik ended the run of Brazil’s Joao Fonseca with a 6-4, 6-3, 7-6 (3) victory.

“It was one of my best performances so far,” Mensik said.

The 19-year-old Fonseca beat 24-time Grand Slam champion Novak Djokovic in five sets in the third round and then eliminated two-time runner-up Casper Ruud in the fourth round.

Mensik collapsed to the clay with cramps upon edging Mariano Navone in a fifth-set tiebreaker in the second round and also needed five sets to advance in the fourth round against Andrey Rublev.