Aryna Sabalenka overcame a tense moment with the umpire to storm into the semi-finals of the Stuttgart Open, while Jelena Ostapenko extended her perfect record against Iga Swiatek in a day full of drama on the clay.

During her quarter-final match against Elise Mertens, world No. 1 Sabalenka found herself at the center of controversy. Facing break point and trailing 4-3 in the first set, Sabalenka strongly disagreed with an "out" call on one of her shots. She requested umpire Miriam Bley to inspect the ball mark, then took matters into her own hands—literally—by walking over and snapping a photo of the disputed mark using a phone from her team.

The move earned her a warning for unsportsmanlike conduct, but Sabalenka quickly regained her focus. She broke back immediately and never looked back, ultimately winning the match 6-4, 6-1.

At the net, there was noticeable tension between Sabalenka and umpire Bley. In her post-match interview, Sabalenka remarked, "When I gave her a handshake, there was a very interesting look and a very strong handshake. Never had it before." When asked if she returned the squeeze, she replied, "No, it's OK. Why would I play this game with someone like her? It’s OK."

Sabalenka now awaits the winner of the match between Coco Gauff and Jasmine Paolini for a place in Monday’s final.

Elsewhere, Jelena Ostapenko delivered one of the biggest shocks of the tournament by beating world No. 2 Iga Swiatek 6-3, 3-6, 6-2. The victory marked her sixth straight win over the Polish star, making her the first player to defeat Swiatek on grass, hard, and clay courts.

Swiatek, a two-time Stuttgart champion with an 11-1 record at the event before this match, struggled once again with Ostapenko’s aggressive groundstrokes. The Latvian fired 29 winners to Swiatek’s 17 and capitalized on eight double faults from her opponent.

Ostapenko started strong, breaking Swiatek three times in the first set. Although she dropped the second, she raced through the deciding set, winning 12 of the first 15 points to secure the win. “She’s a great clay-court player, but I won the French [Open] too, so I can say the same thing about myself,” Ostapenko said afterward. “Every time we play, it’s a battle—and I’m ready for it.”

Ostapenko will face Russia’s Ekaterina Alexandrova in the semi-finals, after the third seed Jessica Pegula fell 6-0, 6-4 in their quarter-final clash.