Casper Ruud survived a fitness scare and a furious fightback from Roman Safiullin to book his place in the second round of the French Open on Monday.

The 2022 and 2023 Roland-Garros runner-up looked comfortable after winning the first two sets – the second with a commanding tie-break showing – and he was on the brink of a routine victory when he generated five match points in the third.

However, Safiullin saved each of them – two on his own serve and three against Ruud's serve – before recovering a break and serving out the third set.

From that moment on, the stifling heat in Paris started to affect Ruud as he called two medical timeouts and had his temperature checked.

Ruud repeatedly used his racket to steady himself and shook his head between points as Safiullin recorded a fourth-set bagel, seemingly making himself the clear favourite ahead of the decider.

But the Russian called a medical timeout of his own near the end of the fourth set, and that extra pause seemed to boost Ruud's recovery as he came roaring back in the fifth, breaking in game four and again in game eight to seal a 6-2 7-6 (7-5) 5-7 0-6 6-2 win.

"I was close to being on the way home," Ruud said after almost four hours on the court. "In the end of the third and fourth sets, I felt quite horrible and dizzy. It was really hard to see the ball. 

"Luckily, I was able to give myself some time to breathe in the fourth set, to see if I could calm down and let the high temperature ease off. It was a really tough match."

Ruud will face Hamad Medjedovic in the next round, while fifth seed Ben Shelton will take on Belgium’s Raphael Collignon after beating Daniel Merida 6-3 6-3 6-4 on Monday.

Shelton, who had endured a difficult spell on the clay coming into the second grand slam of the year, has now won 13 of his 15 opening-round matches at the majors, last falling at the first hurdle at Roland-Garros three years ago.

Fellow American Tommy Paul also advanced, teeing up a meeting with Lorenzo Sonego by overcoming Rinky Hijikata, while Andrey Rublev defeated Ignacio Buse, both in four sets.

Data Debrief: Ruud finds a way

Ruud looked to be on his way out of his favourite grand slam after giving up the fourth set, barely managing to lift his racket in response to Safiullin's serves as he battled a high temperature.

But after finding a second wind, Ruud has now celebrated 25 of his 53 grand slam main-draw victories at Roland-Garros (47.2%).

Among the 22 currently active players on the ATP Tour with at least 50 victories at the majors, that share is the highest anyone has managed at the French Open.