Adrian Mannarino saved a match point to defeat top seed Andrey Rublev at the Kremlin Cup on Thursday, avenging his defeat to the Russian in the Moscow final two years ago.
France's Mannarino, 33, triumphed 5-7, 7-6 (7/4), 6-3 over the world number six to reach the quarter-finals.
"Two years later, it is completely different," Mannarino said in his on-court interview.
"We have both improved. Andrey has improved a lot more than me. Even if a player is better than you, anything can happen. I got a little bit lucky today and I am really happy with my performance."
Meanwhile, Maria Sakkari on Thursday became the first Greek woman to qualify for the season-ending WTA Finals.
Sakkari joins Ashleigh Barty, Aryna Sabalenka, Barbora Krejcikova and Karolina Pliskova in the singles field in Guadalajara.
She ensured qualification when Russia's Anna Kalinskaya retired from their second round match at the Kremlin Cup.