PARIS (AP) — For Stan Wawrinka, it was just one of those days when you smash your racket. Or hit your head with it.

Nothing went right for the 2015 French Open champion as he lost in straight sets to Rafael Nadal in Sunday's final at Roland Garros.

"I think from the beginning from my side, for sure, I didn't play my best tennis," Wawrinka said. "I think I was a little bit hesitating with my selection of shots. I was always, like, a little bit between for few reasons.

"One, because I play against him and he puts this doubt in your head when you play against him because he's playing so well. And second, all the effort I have been doing last few weeks to get to my best level again, to get some confidence again, and to win all those matches, some tough matches. So many reason made that score today, but mainly because he was playing better."

Nadal dominated as beat third-seeded Wawrinka 6-2, 6-3, 6-1 in just over two hours to become the first player to win 10 championships at the same major in the Open era.

"There is many things I can talk about the game, about what I did, about what he was doing, that I should have done or tried differently, but in the end of the day, I think it's quite clear the score," Wawrinka said.

Wawrinka, who has three major titles, had never lost a Grand Slam final but was clearly struggling to come up with answers to Nadal's clay-court prowess.

The 32-year-old Swiss hit his head with his racket several times during the match, while he also smashed his racket after giving up two set points to Nadal at the end of the second.

"I was trying to find solution," Wawrinka said. "I was trying to play better. I was trying to play the game I wanted to play. I was trying to do something different.

"But there is not much to talk about the match. I think tough match, tough loss. I played against the biggest clay-court player ever. He won his 10th French Open today, so that's something huge, also."

Despite being up against the undisputed king of clay, Wawrinka came into the final full of confidence after beating top-ranked Andy Murray in the previous round.

Wawrinka, who triumphed in Geneva in the buildup to the tournament, had also won a career-high 11 successive matches on clay.

And the Swiss player is hoping to take that form into the grass-court season.

"For sure this score wasn't good, the match wasn't good, but at the end of the day there's a lot of positives to take from the last few weeks," Wawrinka said.

"There is many, many, many good things. Two weeks or three weeks ago I was really down, not winning matches in Masters 1000, not playing my best tennis, a lot in doubt in my game when I was playing. In three weeks I won Geneva and made final of a Grand Slam, so that's big for me. That's for sure."