Seventh seed Andrey Rublev said he was "unlucky" in his surprise five-set loss to Jan-Lennard Struff in the French Open first round on Tuesday.
In-form Russian Rublev, who beat Rafael Nadal en route to the Monte Carlo Masters final earlier this season, fought back from two sets down before succumbing 6-3, 7-6 (8/6), 4-6, 3-6, 6-4 in three hours and 46 minutes.
The 23-year-old, who had reached the quarter-finals in each of his previous three Grand Slam tournaments, was the third-highest seeded player in his half of the draw, behind Novak Djokovic and Nadal.
"Of course I was thinking that I would like to come back from 2-0 (down), but I don't know, the fifth set I was a bit unlucky," said Rublev.
"He's a really tough opponent for the first round, really tough, plus he's playing better and better.
"But I think I played good level. Was many good rallies, good intensity. Was really unlucky."
Big-hitting German Struff will face Argentina's Facundo Bagnis in the second round after beating a top-10 player for the ninth time in his career, but for the first time at a major.
"Very happy I won 6-4 in the fifth, and definitely it's a huge win for me in a Grand Slam against a top-10 player," said the world number 42. "Yeah, very, very important."