Defending champion Andrey Rublev stunned in Monte Carlo, Jannik Sinner strolls through

Popyrin broke in the third game of the first set, but Rublev broke to take a 3-1 lead in the second, only for the Australian hit back immediately.

A further break made it 5-4 to Popyrin and he held serve to reach the third round for the first time. Russian fifth seed Rublev had received a bye into the second round.

"The idea was not to give him the same ball," Popyrin said.

"He is probably the best player from the baseline when you give him rhythm, so I tried to change the pace, height and spin and I think it worked really well for me today."

Popyrin will face fellow Australian Alex de Minaur next, after the 11th seed beat Dutchman Tallon Griekspoor 2-6, 6-2, 6-3.

Italian Sinner, who won his first major title at the Australian Open in January, eased into the third round with a 6-1, 6-2 win over American Sebastian Korda.

Korda won their last meeting, in Adelaide last year, but was no match for the in-form Sinner, who also won this year's Miami Open and Rotterdam Opens.

Sinner, who broke Korda in the opening game of the match and was never threatened, will next meet German Jan-Lennard Struff who he beat at Indian Wells in March.

Russian fourth seed Daniil Medvedev came through against Gael Monfils 6-2, 6-4, but was given a tough test by the French 37-year-old in the second set.

Monfils led 4-1, however, Medvedev recovered and won five games in a row to avoid a third set, but not before a disagreement with the chair umpire Mohamed Lahyani.

The Russian was clearly angry with a decision, whacking the umbrella over his seat, and when Lahyani said he would apologise if he was wrong, it only increased Medvedev's frustration.

"How can you apologise, I lost the freaking game, it's a freaking sport man. You guys are getting ridiculous, with the Hawk Eye live you don't see anything," Medvedev said.

After the game, Medvedev shook hands and apologised to the umpire, and later explained the situation.

"I am happy I managed to at one moment try to stay calm, to get my composure, that's what I wanted to do more this year," he said.

"There are going to be moments when I still go crazy... but I am 99% sure the ball was out. It's a pity because I would have won the game and maybe I win 6-2, but I am happy that even from 4-1, I managed to come back and win the set."

Two-time champion Stefanos Tsitsipas, the 12th seed, also reached the third round after crushing Tomas Etcheverry of Argentina 6-1, 6-0 and will next face German fifth seed Alexander Zverev.

French 14th seed Ugo Humbert defeated China's Zhizhen Zhang 6-1, 6-4, and will face Lorenzo Sonego in the third round after the Italian, brought in as a lucky loser to replace the injured Carlos Alcaraz, beat Canada's Felix Auger-Aliassime 6-4, 7-5.

Russian Karen Khachanov came from a set down before seeing off Argentine Francisco Cerundolo 4-6, 6-4, 6-3 to advance to the third round.