MONACO -- Rafael Nadal is unsure how his latest injury return will go this week, even though it will be on the clay-court king's favorite surface.
The second-ranked Spaniard is coming back at the Monte Carlo Masters, a tournament he has won a record 11 times along with the French Open and Barcelona.
"It has been a tough year and a half for me, so it's tough to have a clear view about how I am," Nadal said Monday at the French Riviera tournament, where he plays Spanish countryman Roberto Bautista Agut in the second round on Wednesday.
"I had too many stops; I didn't find a way to play three weeks in a row without problems. So it has been hard for me. When you have these things going on, on the mental side it's up and down. It's always like a comeback."
Even Toni Nadal, his uncle and former coach, was skeptical about Nadal's long-term future in tennis in an interview with El Pais last month.
"Rafael wants to continue playing, despite his physical problems," Toni said. "That is what will continue to be decisive. Until when, who knows? Maybe two or three more years. What I'm saying is that Rafael is not a tennis player, he's an injured person who plays tennis."
Responding on Monday, the 32-year-old Nadal said his uncle had apologized for the comments.
"He came to the court and felt sorry for that. Toni wanted to say it in a positive way because of course I had many issues," Nadal said. "Toni has conferences for companies every week. So when you talk a lot, sometimes you make some mistakes."
Bautista Agut beat top-ranked Novak Djokovic at the Miami Open last month — where Nadal did not play. His troublesome right knee had flared up again the previous tournament, forcing him to pull out of his semifinal against Roger Federer at Indian Wells.
Nadal resumed practice two weeks ago and his knee is holding up.
"My knee is quite good. Happy for that. Now I need to work on the tennis," he said. "I hope the competition puts me in the rhythm I need."
Nadal usually finds his rhythm quicker than anyone on clay.
Last year, he missed February and March after retiring in the fifth set of his Australian Open quarterfinal against Marin Cilic with a hip injury.
However, it did not stop him reeling off 14 straight wins on clay without dropping a set — winning two Davis Cup matches, the Monte Carlo and Barcelona titles before Dominic Thiem stopped him in the Madrid Masters quarterfinals.
Nadal went on to win the Rome Masters and French Open and reached the Wimbledon semifinals on grass, losing an epic five-setter to Djokovic.
Then his body let him down, again.
After retiring from the U.S. Open semifinals against Juan Martin del Potro because of a right knee injury, he did not play again last season — pulling out of the Paris Masters and the season-ending ATP Finals with an abdominal problem.
"I don't like to talk about frustration," Nadal said. "Because life has been too good to me to be frustrated."
Nadal has won more than $100 million in prize money and 80 titles, including a record 33 Masters events. His tally of 17 Grand Slams is second to Federer's 20.
But nagging doubts persist.
"At some point, even if I appreciate everything this sport has given to me, sometimes it's tough to accept when you have problems in a row," he said. "Since the beginning of the season again it has been tough. You need to be strong mentally and keep the passion very high."
But Nadal did manage a lighter note about his uncle's "overdramatic" prognosis.
"Being No. 2 in the world, it is maybe difficult to be where I am being an injured person," Nadal said, smiling. "I have more problems than almost the rest of my competitors, but I was able to manage it well all my life."
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