Stan Wawrinka claimed his physical toils during his French Open first-round defeat to Guillermo Garcia-Lopez on Monday were not related to his pre-existing knee injury.

The 2015 champion, and last year's runner-up, fell at the first hurdle this time around, beaten 6-2 3-6 4-6 7-6 (7-5) 6-3 by the Spaniard, who will meet Karen Khachanov in the next round.

Wawrinka appeared to be struggling at an early stage in the match, calling for a medical time-out at the end of the first set, but the Swiss allayed any fears the problem was a recurrence of the issue that forced him to have surgery in 2017.

"I think my knee is fine," he told his post-match news conference. "My knee is good.

"I blocked something else at the beginning of the first set, and that's why I had to ask [for a time-out], because it was completely blocked.

"But since the physio just manipulated it a little bit and it was completely fine."

Wawrinka reiterated that it was "completely" unrelated to his pre-existing problem and said he was in no pain after the contest.

"So that's the positive of today," he said. "As I say, my knee is good. I'm happy with that. That's really positive to see, but it's been now a few weeks that I'm feeling great with that sort of injury I did. So that's good. I'm in the right way, and I need to keep pushing.

"I realised that something was blocked but was not at all something about the same knee, about my knee.

"It was something completely on the side. So I just wanted to fix it, because it was really strange pain."