Top-ranked Daniil Medvedev committed 11 double-faults in falling to Stefanos Tsitsipas 7-6 (8/6), 3-6, 6-3 in the semi-finals of the ATP and WTA Cincinnati Masters.
Fourth seed Stefanos Tsitsipas has edged world number one Daniil Medvedev 7-6(6) 3-6 6-3 in an absorbing semi-final at the Cincinnati Open to set up a summit clash with Borna Coric after the Croatian's 6-3 6-4 win over Cameron Norrie.
Medvedev on Saturday helped seal his own fate in the sixth game of the final set as he double-faulted four times to hand his Greek opponent to a 4-2 lead.
Tsitsipas will play for the title on Sunday against Croatian Borna Coric, who returned to an ATP Masters final for the first time in four years by defeating Britain's Cameron Norrie 6-3, 6-4.
Tsitsipas won only his third match against Medvedev after losing seven and also defeated a reigning number one player for only the second time in 12 career attempts.
The fourth seed put a winner into the corner on the first of three match points to earn the final.
"I knew I would have a difficult task in the third set," Tsitsipas said. "He made it a very physical match, very demanding.
"But I took advantage of his missed first serves. They gave me time to think of my next move clearly. I was very calm and concentrated on every single task."
World number 152 Coric, who missed a year of play with shoulder problems and only returned to the tour in March, advanced in 91 minutes in a match delayed for hours by an afternoon of rain.
On the women's side, Petra Kvitova outlasted Madison Keys 6-7 (6), 6-4, 6-3 on Saturday to reach the Western & Southern Open final.
The 32-year-old Kvitova had never advanced to the semifinals in 10 prior appearances in the Cincinnati tournament. It is Czech's 40th career final, and she'll face another surprise entrant in Frenchwoman Caroline Garcia, the first qualifier to reach the final in Cincinnati.
Kvitova almost didn't make it out of the first round, having to save a match point against last year's finalist, Jil Teichmann. She also needed three sets to beat fifth-ranked Ons Jabeur in the third round.
Keys, the 2019 champion in Cincinnati, defeated three grand slam winners this week, but couldn’t close out Kvitova.