Does Rafael Nadal remain the King of Clay?

That's the big question surrounding the 14-time Grand Slam winner as the world's best players gather in Monte Carlo this week for the first Masters of the season played on clay.

Relaxed, tanned and smiling, the former top-ranked Nadal looks more than happy to return to his favorite surface after a mediocre start to the season during which he believed he was in the worst form of his life.

The Spaniard has a 15-5 record in 2015, having lost in the quarterfinals at the Australian Open after recovering from a wrist injury and an appendectomy. After that, he enjoyed a good week in Buenos Aires where he won the title in February but then struggled on the hard courts of Indian Wells and Miami.

"This tournament marks the start of my favorite part of the season," Nadal told reporters Sunday as he bids for a ninth title in Monte Carlo. "I know that I have to play better than what I did. I'm working to be playing well again as soon as possible. If I did not believe in my chances, I would not be here. I would be doing other stuff, because I already achieved all the things I needed to do in my career. I still have the passion and motivation to keep playing tennis."

Nadal, who has dropped to fifth in the rankings, returned to Spain to practice at home after his loss to Fernando Verdasco in Miami. He believes the small adjustments he made to his game are likely to pay off and to help him play with more consistency and confidence.

"For me, the most important is the mental part, because I don't think I forgot how to play tennis," said the 28-year-old Nadal, while smiling. "From playing bad to playing well, there is not a very big difference. It's just small things that make big changes. If I'm well mentally, if I can play with a little bit more confidence, it will be easier to hit better shots."

Monte Carlo is the first of three Masters tournaments played on clay and is followed by Madrid and Rome, leading up to the French Open, which starts May 24. Nadal said Roland Garros, where he has reigned supreme over the last 10 years, "is not in my mind at the moment."

He has been handed a difficult draw in Monte Carlo, with a potential quarterfinal match against David Ferrer, who beat him last year at the same stage of the tournament, and a possible semifinal with top-ranked Novak Djokovic.

Djokovic, like Nadal's other rivals, is not giving too much importance to the Spaniard's current struggles. For them, he remains the man who won the French Open nine out of the past 10 years.

Defending champion Stan Wawrinka listed Nadal alongside Djokovic as the French Open favorites and the Serb has no doubt about his soon-to-be recovery.

"Whenever the clay court season comes around, he is the first player to be mentioned as the favorite in any tournament," said Djokovic. "He is called the 'King of Clay' and he deserves that crown, He has lost only one match in Roland Garros, and he is an ultimate challenge. Even though he has struggled with injuries and lack of matches, it's Nadal and this is his surface."

While Nadal has not won a big tournament since last year's French Open, Djokovic became the first man to complete the Indian Wells-Key Biscayne spring sweep three times earlier this month. The injury-prone Djokovic admits he is tired after his tremendous start to the season but remains confident the fitness work he did during the offseason will help him stay healthy.

"It's a positive consequence that I have to pay because of the results that I've made, so I can't complain," said Djokovic, who hopes to achieve a career Grand Slam at Roland Garros. "Next to 2011 this is definitely the best start I ever had. Hopefully I can follow up because now it's clay-court season. It's completely different from hard court."

Nadal knows that, too.