Rafael Nadal completed his delayed French Open first round match on Tuesday, but the defending champion was made to "suffer" in his straight sets victory over Simone Bolelli.
Nadal, 31, held a two sets lead over his Italian opponent on Monday before rain forced the contest to be completed the next day. With Nadal trailing 0-3 in the third set, the Spanish world No 1 immediately got back on level terms, but was forced to dig deep in the eventual tie-break, fending off four set points before closing out a 6-4, 6-3, 7-6 victory in just over three hours.
Nadal, who is bidding to win a record-extending 11th Roland Garros title, will next face Guido Pella after the Argentine produced a straight sets win over Portugal's Joao Sousa.
"I really suffered today but it was a good test," Nadal said. "It was very difficult. Simone is a very good player and he had lots of chances and was very aggressive.
"But I am happy to have won here on this court, the most important of my career."
However, Nadal was far from happy with the clay on Philippe Chatrier, the court where he has only lost twice in his career.
"The court is more slippery than usual and I slid a lot when I started off or when I moved to another side, and it was quite complicated," he said.
"There are no excuses. This is what I felt. If you look at the images on television, you can see that there are many more whiter zones than other years, because there are little pebbles underneath, and that's why you don't have the proper grip on the court."
Third seed Marin Cilic reached the second round with a 6-3, 7-5, 7-6 win over Australia's James Duckworth.
Wimbledon and Australian Open runner-up Cilic fired 47 winners and 13 aces past world No 1,072 Duckworth, who was playing his first match since the 2017 Australian Open.
The 29-year-old Croatian will take on Poland's Hubert Hurkacz, who booked his place in the second round with a four-set win over American Tennys Sandgren.
Cilic is on course to face Nadal in the semi-finals, but the Croatian is not looking that far ahead.
"It's still very far. If we're going to meet it's going to be in the semis, so still a lot of work to do,” Cilic said. “Rafa is always really consistent and getting his rhythm through the couple matches. He's going to be playing definitely better and better.
“But, you know, I'm just focused on every single match. You can't get ahead of yourself."
Denis Shapovalov eased to a 7-5, 6-4, 6-2 victory over Australian John Millman in his first ever main-draw French Open match.
The 19-year-old Canadian, who lost in Roland Garros qualifying last year but is now the 24th seed, will next take on German world No 70 Maximilian Marterer for a place in the last 32.
"The last couple of weeks I've been playing unbelievable on this surface," said Shapovalov, who reached the semi-finals of the Madrid Masters earlier this month and is the youngest player to break into the world's top 30 since 2005.
British No 1 Kyle Edmund began his French Open campaign with a 6-2, 6-4, 6-3 win over Australian wildcard Alex De Minaur, completing the victory in less than two hours.
Edmund, 23, will face Marton Fucsovics for a place in the third round after the Hungarian earned a straight sets win over Canada's Vasek Pospisil.