Andrey Rublev and Alexander Zverev both survived dropping a set to advance in the Monte Carlo Masters on Tuesday as last year's runner-up Alejandro Davidovich Fokina fell at the first hurdle.
Fifth-seeded Rublev, recipient of a first-round bye, rallied from a set down to defeat Spaniard Jaume Munar 4-6, 6-2, 6-2 in their second-round tie.
Germany's Alexander Zverev made a hesitant start to his clay-court season before seeing off Kazakh Alexander Bublik 3-6, 6-2, 6-4 in the first round.
But Spaniard Davidovich Fokina fell 6-2, 6-2 to ninth seed Karen Khachanov.
Rublev, a losing finalist in 2021, broke Munar's serve six times and hit 36 winners to win in two hours and 12 minutes.
"The feeling was, 'No way, I might be out in the first round of Monaco'," said Rublev, 25, who will next face fellow Russian Khachanov, Dan Evans or qualifier Ilya Ivashka in the third round.
Khachanov took 75 minutes to brush past Davidovich Fokina, who lost the final in the Principality last year to Stefanos Tsitsipas.
Zverev was finding his feet back on clay for the first time since he retired in the French Open semifinals last year against Rafael Nadal with a nasty right ankle injury.
The 13th-seeded German took just under two hours to move past Bublik with 21 winners to nine unforced errors.
"It felt awful at times to be honest," Zverev said.
"It usually takes me five or 10 minutes to get used to a clay court, but this year was a bit different. I needed to get the injury out of my head. I needed to get used to sliding again.
"I have had two weeks of practice now. It is the most natural surface for me."
Zverev, a two-time Monte Carlo semifinalist, will next play Spaniard Roberto Bautista Agut for a place in the third round.
Italy's Lorenzo Sonego saved four match points to beat French qualifier Ugo Humbert 3-6, 7-5, 7-5 and next plays third seed Daniil Medvedev in the second round.