Paris - Roger Federer on Friday played down his chances of winning the French Open on his first appearance at Roland Garros since 2015, saying that title-winning form might not be "in his racquet".
The 20-time Grand Slam champion missed the French Open in 2016 through injury before sitting out the next two clay-court seasons in order to focus on Wimbledon.
But he will make his Roland Garros return on Sunday with a first-round tie against unheralded Italian Lorenzo Sonego.
Federer admitted that he is unsure of his title chances, but did compare his current situation with when he ended a five-year Grand Slam drought at the Australian Open in 2017.
"(I) don't know (if I can win the tournament). A bit of a question mark for me. Some ways I feel similar to maybe the Australian Open in '17," the 2009 French Open winner said.
"A bit of the unknown. I feel like I'm playing good tennis, but is it enough against the absolute top guys when it really comes to the crunch? I'm not sure if it's in my racquet.
"But I hope I can get myself in that position deep down in the tournament against the top guys. But first I need to get there and I know that's a challenge in itself."
Despite being the third seed, Federer faces a tricky draw, with a possible quarter-final against Greek youngster Stefanos Tsitsipas - who beat him in the Australian Open last 16 - and a potential last-four clash with 11-time champion and old adversary Rafael Nadal.
Considering his lengthy absence from the red dirt, the 37-year-old has performed well on clay this year, reaching both the quarter-finals in Madrid and Rome.
Federer saved match points to win against both Gael Monfils in the Spanish capital and Borna Coric at the Italian Open, and thinks those matches will stand him in good stead for the coming fortnight.
"I think I have been able to train hard enough and also got the necessary tough matches in Madrid and Rome, more than I would have liked to, but I guess we like saving match points or trying to lose with match points," he said.
"I really feel like playing under the pressure and playing with the nerves was important for me so I feel totally ready."
Federer was forced to pull out in Rome before his scheduled quarter-final against Tsitsipas with a right leg injury, but he insisted that was just a precaution to ensure he was totally ready for Paris.
"I wanted to make sure I was 100 percent going to be able to play the French Open.
"I just had that doubt, like if I did (play on in Rome) I couldn't. And I didn't like that feeling."
This year's tournament marks 20 years since Federer made his debut in the main draw of a Grand Slam event, when he was beaten in four sets by Pat Rafter in the Roland Garros first round.
It also has been a decade since he ended a long wait to complete the career Grand Slam, when he dealt with mounting expectation to defeat Nadal's conqueror Robin Soderling in the 2009 final.
"Soderling had beaten Rafa... But I knew that instead of the tournament becoming easier, it was going to become more difficult because of the pressure," Federer said. "I feel proud that I was able to manage the pressure."
There is much less pressure on Federer 10 years on as he enters the tournament as a firm dark horse, but a shock early loss for 11-time champion Nadal could yet spark hopes of a fairytale second title.