Rafael Nadal heads into the French Open optimistic his uncharacteristic clay-court struggles are behind him.

The eight-time Roland Garros champion has been near unbeatable on the surface for the best part of a decade but this year that facade of invincibility has started to crack.

He lost in the quarter-finals in both Monte Carlo and Barcelona, to David Ferrer and Nicolas Almagro respectively, and last weekend was beaten by Novak Djokovic in the final in Rome.

It is the first time Nadal has lost three matches in the build-up to the French Open since he first won the title in 2005.

Even the tournament he did win, the Madrid Open two weeks ago, left question marks about his form given his final opponent Kei Nishikori had been in control before being struck down by back spasms.

In Rome, meanwhile, Nadal struggled physically against Djokovic after surviving a number of close matches.

The Spaniard has been open about the doubts that have crept into his mind since his own back problems contributed to his Australian Open final loss against Stan Wawrinka.

Speaking in Madrid, Nadal said: ''When you compete at this level, when you're playing at the limit, sometimes you crash against the wall.

''All the crashes you get during your career, you just have to survive. You just have to try for it not to be a mortal blow."

Nadal certainly projected a more positive air speaking at his pre-tournament press conference in Paris, and he said: "During the clay-court season I get a little bit better week by week.

"Last week in Rome it was tough physically. I played a lot, but in the end sometimes you need these things.

"And I think I played a little bit better during the whole tournament, and especially after the first two rounds, the quarter-finals, semi-finals and final.

"I think I took a positive step, and I'm happy the way that I finished in Madrid and Rome. I'm n ot that happy about what I did in Monte?Carlo and Barcelona, but that's the sport.

"We are here in Roland Garros, and I'm just happy to be back in a place that has given me so much.

"I felt that in Rome I was able to play without nerves, without that anxiety that I played in the first two tournaments and some moments in Madrid, too."

Nadal starts his tournament against American Robby Ginepri while he could face 20-year-old Austrian rising star Dominic Thiem in round two.

Roger Federer also arrived in Paris with question marks over his prospects but for very different reasons.

The 32-year-old is playing his first grand slam as a father of four after wife Mirka gave birth to a second set of twins, Lenny and Leo, almost three weeks ago.

Federer, who lost to Stan Wawrinka in the final in Monte Carlo, played in Rome but lost his first match to Jeremy Chardy.

The Swiss insisted his family situation is not taking too much of a toll on his tennis, saying: " They sleep that much that I don't feel bad yet going out of the room and coming back. It's almost the same situation.

"Clearly there is a bit more happening and there is a bit more you can do if you want to, but Mirka takes care of most of it.

"I hold them as much as I can, but I clearly also want to go out and about with the girls. Routines are pretty much the same really.

"The only difference is that I didn't play a lot in the last couple of weeks. That's usually the weeks either I play better or my best.

"But playing well in Monaco was helpful in the sense that when I went to training I knew what I needed to work on. I feel like I'm in good shape. I know where my game is at."

Second seed Djokovic, who has Federer in his half of the draw, opens his campaign against Portugal's Joao Sousa while third seed Wawrinka faces Guillermo Garcia-Lopez.