Third-seeded Roberto Bautista Agut also advanced after outlasting France's Pierre-Hugues Herbert 6-4, 6-7 (2), 6-1, while Tunisian wild-card entry Malek Jaziri continued his surprising run by beating Dutchman Robin Haase 7-6 (4), 7-6 (3). Jaziri knocked out top-seeded Grigor Dimitrov on Tuesday.

Two more seeded players lost on Wednesday, as Russia's Evgeny Donskoy beat No. 4 Damir Dzumhur 6-1, 6-1 in just 50 minutes and rising Greek star Stefanos Tsitsipas defeated No. 6 Philipp Kohlschreiber of Germany 4-6, 6-3, 6-4.

Pouille saved two break points in the eighth game of the first set, then broke himself in the next game. Khachanov then broke for a 4-2 lead in the second set before leveling the match, but it was Pouille who earned the only break in the decider.

"I knew it would be a tough one. In the final in Marseille, he won just three points more than me. It was very close. I knew I had to play some good tennis," Pouille said. "We were both a little bit tired I think. So, I'm just very happy that I got my revenge today."

Jaziri will face Tsitsipas in the quarterfinals, while Bautista Agut takes on 21-year-old Croatian Borna Coric.