Federer believes he is closer to figuring out how to beat Nadal on clay.

Second-ranked Nadal defended his Monte Carlo Masters title with a 6-2, 6-7 (2), 6-3, 7-6 (5) win over Federer on Sunday, handing the seven-time Grand Slam champion his second defeat of the year.

Nadal has beaten Federer four times in five meetings, and twice on clay after winning in four sets last June at Roland Garros. Federer, who had 78 unforced errors on his least-favorite surface, is now 28-2.

"I was beating him easier today than in Paris," Nadal said. "To begin the clay season like this, for me, is unbelievable."

Spanish tennis player Rafael Nadal poses during a photocall at the Barcelona Open in Spain, April 24, 2006. [Reuters]

Nadal extended his winning streak on clay to 42 matches and can pass Bjorn Borg's mark of 46 and move behind Guillermo Vilas (53) if he wins next weekend at Barcelona.

"One day, for sure, I'm going to lose on clay," said Nadal. "I just hope it isn't next week."

Federer complimented himself on "a fantastic week" and felt his chances of one day overhauling Nadal on clay "went up."

"I've got to adjust quite a bit to play Rafael," Federer said. "But I already feel like I'm improving a lot. The more I play against him, the more I'll be able to figure out his game and the easier it will be."

Nadal broke Federer seven times, overcame a 3-0 deficit in the fourth-set tiebreaker and won the match with a forehand pass that bounced on the line.

"It's very special for me to defend the title," Nadal said. "Beating Federer in a final is special too. I was very aggressive with my forehand and I had a good touch."

Federer lamented missed opportunities, felt his serve was below par, and was upset at converting only 4-of-18 breakpoint chances.

"I was not serving well enough or just playing well enough from the baseline," Federer said. "I thought I gave him a little too much."

Nadal used his big forehand to pressure Federer on his weaker backhand.

"He's a lefty, so I'm always going to have problems," Federer said. "I enjoyed the battle against him. I have answered some questions I had about how to play on clay."

Federer appeared in his 12th consecutive final, but his winning run in Masters series matches ended at 29. His previous Masters defeat came at Monte Carlo in a quarterfinal loss to Richard Gasquet of France last year.  

Federer started with a string of erratic shots that helped Nadal race to a 4-0 lead.

He finished with twice as many unforced errors as his opponent, and his first-set loss was the largest margin this season. Federer's previous worst sets were 3-6 against Olivier Rochus, Nikolay Davydenko and Tommy Haas.

"I don't care about the unforced errors, as I had no choice but to attack him," Federer said. "I'm going to make errors because I'm the guy pressing."

Nadal served for the second set at 5-4, but Federer broke him, and closed out the tiebreaker with an ace. At the start of the third set, Federer broke Nadal to love and looked comfortable on serve before suffering a lapse.

"I thought I let him have a couple of breaks, you know, just stuff out of the blue really," Federer said.

Nadal broke for a 5-3 lead, and Federer screamed in frustration while losing the next game.

Early in the fourth set, Federer called himself an "idiot" after one backhand shot looped out. He trailed 3-0, rallied to a 5-4 lead, but Nadal easily won his two service games to force a tiebreaker.

He arched his back in triumph and pumped his fists when his forehand pass bounced in on match point.