Defending champion Stefanos Tsitsipas and second seed Alexander Zverev posted straight sets wins on their way to the Monte Carlo Masters quarterfinals on Thursday, while fourth seed Casper Ruud was knocked out in straight sets by Grigor Dimitrov.

Tsitsipas dispatched Serbian Laslo Djere 7-5, 7-6 (7/1), and German Zverev fired eight aces and smashed 26 winners to beat Spaniard Pablo Carreno Busta 6-2 7-5 on the back of a strong first serve. 

Tsitsipas, the world No. 5, will play Diego Schwartzman for a place in the semifinal after the Argentine 12th seed fought back from a set down to beat Lorenzo Musetti 2-6 6-4 6-3, receiving a standing ovation from the crowd after the 2-1/2-hour contest.

"I had to put in a very good performance," said Tsitsipas, who lost in five sets to Novak Djokovic in the French Open final last year. 

"Laslo did not hand me victory, but I tried to stay 100 percent focused," added the 23-year-old Greek.

Earlier, Norwegian Ruud became the tournament's latest high-profile casualty as he went down 6-3 7-5 to Bulgarian Dimitrov, who moved into the quarterfinals for the fourth time. 

"It's always tough this week because you're switching surfaces," Dimitrov said. "So, I try and not be too tough on myself in practice. I just try to do the simple things. It's going so well so far." 

Unseeded Spaniard Alejandro Davidovich Fokina, who upset world No.1 Djokovic earlier this week, reached the last eight with a 6-4 6-1 win over David Goffin. 

He will meet 10th seed Taylor Fritz, who beat doubles partner Sebastian Korda 7-6(4) 7-5 in a battle of Americans.

(With input from agencies)

(Cover image: Stefanos Tsitsipas of Greece celebrates after beating Serbian Laslo Djere during the Monte Carlo Masters, Monaco, April 14, 2022. /CFP)