The quarterfinals of the Porsche Tennis Grand Prix saw No.6 seed Marketa Vondrousova defeat No.2 seed Aryna Sabalenka for the first time in six years, winning 3-6, 6-3, 7-5 in 2 hours and 1 minute. 

The Czech advances to the semifinals of a tournament for the first time since winning her first Grand Slam title at Wimbledon last year, and notches her first Top 5 victory since defeating Jessica Pegula in the quarterfinals of that event.

Vondrousova will next face Marta Kostyuk of Ukraine, who won her third straight three-set thriller of the week by toppling No.3 seed Coco Gauff in a third-set tiebreak. Vondrousova won their only previously contested meeting 6-2, 6-1 at Billie Jean King Cup Qualifiers last year.

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Vondrousova had won her first two pro encounters with Sabalenka, but then lost four in a row between 2018 and 2023. However, this was the first time the pair had played on clay, a surface where 2019 Roland Garros finalist Vondrousova has had a significant proportion of her success. The result marks the first time Sabalenka has fallen before the final in Stuttgart, having been runner-up to Ashleigh Barty in 2021 and then to Iga Swiatek in 2022 and 2023.

The match was the second clash between reigning Grand Slam champions this season so far, following Sabalenka's defeat of Coco Gauff in the Australian Open semifinals. It is Vondrousova's first win in four such matches, while Sabalenka's record is 2-4. Previously, Vondrousova had lost to Iga Swiatek at Cincinnati and the WTA Finals Cancun last year, and to Gauff in Cancun as well.

Match moments: In an up-and-down contest that featured 13 breaks of serve and little in the way of momentum, it was Vondrousova's stability and efficiency in important moments that saw her get over the line.

Sabalenka struck 35 winners to Vondrousova's 17, but also committed 48 unforced errors compared to 19. Moreover, the Wimbledon champion had a clinical break point conversion rate of seven from eight, while Sabalenka converted six from 15.

Crucially, though defense was the bedrock of Vondrousova's game against the erratic Sabalenka, she was also willing to take the play into her own hands when she needed to. The 24-year-old's finest stretches were the start of the second set, where she leapt out to a 4-1 lead in a flurry of return winners, drop shots and heavy forehands; and the final three games from 5-4 down in the decider, during which she found a pair of key volley winners.

Indeed, the second of those -- a twisting stab volley to break Sabalenka for 6-5 -- may have been Vondrousova's single best shot of the day.

Vondrousova also showed resilience to withstand the battling Sabalenka, who found her best tennis when behind in the third set. Twice Sabalenka levelled the score from a break down, lasering breathtaking backhand winners down the line. However, she never found any sustained form; and with nine total double faults, her serve became increasingly unreliable as the match progressed.