Third-ranked Alexander Zverev beat Pablo Carreno Busta 6-2, 7-5 at the Monte Carlo Masters to reach the quarterfinals of the clay-court season opener in Monaco.
Carreno Busta broke Zverev to open the second set and built a 3-1 lead before the German rallied, setting up a quarterfinal match against Jannik Sinner.
"I have lost focus a little bit in the second set,” Zverev said.
He then played more aggressively, adding: “I am not going to win big titles just by pushing the ball.” Defending champion Stefanos Tsitsipas advanced by beating Laslo Djere 7-5, 7-6 (1). The fifth-ranked Greek will meet Diego Schwartzman of Argentina in the quarterfinals.
"I really had to work hard for this win,” Tsitsipas said.
Sinner beat eighth-ranked Andrey Rublev 5-7, 6-1, 6-3 to advance, winning six straight games in the second set and dominating the decider before wrapping it up with his seventh break.
"I tried to win every play, every point,” said the 20-year-old Italian, who reached the quarterfinals in Miami last month before retiring from the match against Francisco Cerundolo.
Indian Wells winner Taylor Fritz reached the quarterfinals by defeating doubles partner Sebastian Korda 7-6 (4), 7-5.
Fritz will meet Alejandro Davidovich Fokina, who stunned top-ranked Novak Djokovic on Tuesday. The Spaniard beat David Goffin 6-4, 6-1 to advance on Thursday.
Grigor Dimitrov also advanced by upsetting seventh-ranked Casper Ruud 6-3, 7-5.