Murray has to work to book meeting with Del Potro

The British player, seeded number 1 for the clay court tournament, started sluggishly and fell to a defeat in the first set tie break, before finding his feet to power through the next two sets. 

Murray looked to be in trouble again in the fourth, as Klizan smashed more of his 57 winners but after being a break down for much of the set, the Brit broke back at the last before putting the match to bed in a tiebreak.

"I expected a tough match. Martin goes for his shots, he can hit winners with that forehand from anywhere on the court," said 2016 runner-up Murray. "I tried to play a solid match, I hit deeper the longer the match went on and tried to dictate the points."

De Potro, who lost to Murray in the gold medal match in Rio, experienced a slightly more unusual progression, with the Argentine also living up to his reputation as a player with a big heart.

His opponent Nicolas Almagro collapsed to the court in tears at 1-1 in the third set after succumbing to injury before  Del Potro quickly hurdled the net to console him.

 "Today I think I got lucky, because I don't feel good enough with my body, and then Nico felt something wrong in his knee and he decides to retire," said Del Potro above, in light blue), who had taken the first 6-3 before Almagro claimed the second by the same score. 

"It's an unpleasant feeling. You have a player who is suffering quite a lot. He was in agony. It was tough. I told him that tennis is important, but health matters more than tennis in this case."

Elsewhere, Russian Karen Khachanov defeated 13th seed Tomas Berdych 7-5 6-4 6-4 in probably the shock of the day in the men's draw, while Kei Nishikori and Stan Wawrinka also progressed.

Kasatkina wins Czech contest

In the women's draw, Daria Kasatkina defeated Marketa Vondrousova 7-6(1) 6-4 in a battle of next-generation Czech youngsters. The 20-year-old reached the third round at Roland Garros for the second consecutive year.

There was also joy for home favorite Alize Cornet, who recovered from 4-2 down in the first set to bag a 6-4 6-1 win over Barbora Strycova of Czech Republic.

Things weren't quite so straightforward for ninth seed Agnieszka Radwanska, who needed nearly two and a half hours to beat Belgian qualifier Alison Van Uytvanck 6-7(3) 6-2 6-3. She'll play Cornet in the last 32.

mp (Reuters/AP)