All tennis greats have come up against the limits of their talent. For serve-and-volley masters John McEnroe and Pete Sampras, winning on clay proved too much. For Ivan Lendl, the grass courts of Wimbledon were oh-so-close to being conquered, but not quite. And while Andre Agassi has won on every surface, he has had to play the role of spoiler to dominant players like Sampras and Roger Federer.

One can hardly say that 24-year-old Federer, perhaps on his way to becoming the greatest of the greats, has reached his limit, but it’s clear there is one problem that the otherwise invincible world no. 1 cannot quite solve. For the last year, the man who does everything well has been perplexed by the 19-year-old Spaniard Rafael Nadal, whose arsenal consists, for the most part, of two weapons: a ferocious topspin forehand and his feet.

At the final of the Monte Carlo Masters yesterday, tenacity and simplicity of style again got the better of variety as Nadal walked off the winner, ending a three-hour, 49-minute match with a crosscourt forehand on the sideline for a 6-2,6-7(2),6-3,7-6(5) victory. Nadal has now beaten Federer in four of five matches, won this tournament two straight years, and taken his last 42 contests on clay, a record bettered only by Bjorn Borg (46) and Guillermo Vilas (53). After the first stop on the road to the French Open, the defending champion is still the man to be reckoned with.

“I was beating him easier today than in Paris,” Nadal said, referring to his semifinal victory over Federer at Roland Garros last year. “To begin the clay season like this, for me, is unbelievable.”

Federer sounded an optimistic note, too, saying he had moved a step closer to understanding how to defeat his most challenging opponent. “The more I play against him, the more I’ll be able to figure out his game and the easier it will be,” he said.

Though both men played patchy tennis at times, the match was thoroughly enjoyable. On fast hardcourts and grass, Federer need not flash all his skills to win with relative ease – a few dozen forehand blasts and consistent serves will suffice. But for a man who has no interest in trading groundstrokes from five feet behind the baseline, slower clay courts demand more flourishes and greater attention to tactics. Against Nadal, those demands are increased tenfold. The left-handed Spaniard rarely misses, and the incredible topspin he imparts on his forehand sends lots of balls bouncing up around Federer’s eyes on the backhand side.

To say clay is Federer’s worst surface is an accurate yet misleading statement. He proved again this week that he swings and slides on it as comfortably as anyone. And as enjoyable as Federer is to watch on any given day, he is more so on clay. He approaches more often, shortens points with volleys, slices the occasional drop shot, and, at times, plays serve-and-volley. When Nadal stands across the net, Federer pushes himself to do even more.

After a ragged first set yesterday, Federer showed Nadal everything. He drew the Spaniard to the net with drop shots (this rarely proved successful against the speedy Nadal). His backhand volley, which he has called one of his weaker shots, was superb, including several ankle-high stabs that ended in softly spun winners. After falling behind in the second set, he saved set point and captured the tiebreak. He broke serve to start the third set, gave it back, and had a chance for another at 3-3 when his backhand, always less reliable against Nadal’s spin, failed him again on an easy stroke.

Nadal rattled off the next six games before Federer evened the score at 4-4 in the fourth set. In the final tiebreak, Federer seemed on the verge of a breakthrough. He played three beautiful points – a backhand volley winner set up by a difficult overhead, a backhand approach and forehand volley, and a forehand crosscourt winner in full slide – on his way to a 4-2 lead. But he soon misfired on an easy forehand volley and a forehand cross-court – his 78th error in all, compared to 39 for Nadal. In the end, too many errors and some poor serving games cost him the match and the title.

So, which player was right in his postmatch analysis? Nadal may have won this one more easily than he did in Paris, and he did it in his first clay tournament since last year. Still, one has to be equally impressed with Federer’s attempt to refine his strategy. He knows how to attack Nadal, and seems confident that he can improve at it. There can be little doubt that Federer will be playing better come the French Open, and he may yet have a crack at Nadal in Rome or Hamburg (Nadal plays in Spain this week while Federer rests). Perhaps by then Federer will be the one pushing Nadal to show him a new trick or two.

tperrotta@nysun.com