In his three plus years as the world’s best tennis player, Roger Federer has had many moments where he seemed infallible. He handed Lleyton Hewitt two love sets in the 2004 U.S. Open final, as if the former U.S. Open and Wimbledon champ was a boy fresh out of high school. On the same stage the following year, he snuffed out an Andre Agassi rally late in the third set and dispatched the aging legend in the fourth, dropping only one game. Remember the new and improved Andy Roddick at this year’s Australian Open? Federer turned their semifinal meeting into a shot-making exhibition worthy of the Harlem Globetrotters, at one point winning 11 consecutive games.

Before yesterday’s final at the Hamburg Masters, however, Federer had never performed his magic act on Rafael Nadal. The 20-year-old Spaniard, a masterful defender and a man of few errors, had beaten Federer in seven of their 10 meetings, and even when he lost, he had never failed to frustrate his rival with his high-bouncing, lefthanded forehand. On clay, Nadal had won all five times, including the 2006 Rome final in which Federer, playing as well as he could, squandered two match points in the fifth set.

In Hamburg, at long last, Federer came up with the goods. A week after playing his worst match of the season and firing his coach, Tony Roche, the world no. 1 recovered from a sloppy first set to play his best hour of tennis this season, 2–6, 6–2, 6–0. The last two sets were a sustained catharsis: winners by the bunch, aces, deft volleys, booming returns of serve, and a lucky bounce off the net cord to boot. Only seven points lasted 10 strokes or more. After winning 81 consecutive matches on clay, Nadal suffered his first knockout on the surface since 2005.

The importance of this victory cannot be understated. While Federer had inched closer to Nadal on clay in 2006, this year he was moving in the opposite direction. Filippo Volandri, an Italian of limited ability, abused Federer at the Rome Masters, and Federer did not look much better in Hamburg before the final. He scored a straight-set win against Juan Carlos Ferrero, but dropped sets to Juan Monaco and David Ferrer. In the semifinals, Carlos Moya took the first set before Federer decided he wouldn’t hit every ball to Moya’s forehand (the difference between Moya’s forehand and backhand is a touch shy of infinity).

If he had lost yesterday, Federer, 25, might have arrived at this year’s French Open, which begins next week, with little to no confidence. Now he’ll feel every bit like the world’s best player. Amazing what two sets can do — especially when they follow a set as poor as the first one of this final.

For Federer, bad tactics and poor form were on display from the first game. He didn’t attempt to move forward; he shanked forehands; he couldn’t connect on his first serve, and he faced break points in his first three service games (and lost two of them). Nadal won easily without playing too well. More troubling was the fact that Federer looked helpless. He didn’t put any pressure on Nadal and managed three forehand winners against 10 forehand errors.

So bad was Federer that I’m surprised at how quickly he turned this match around — and that he did so by following the advice of the coach he had just dismissed. To beat Nadal, Federer has to play close to the baseline and shorten the court, create angles, and move to the net when opportunities arise. He couldn’t have executed these tactics better in the last two sets. He went after Nadal’s forehand more often, forcing the Spaniard to abandon the backhand corner he prefers. When Nadal establishes position there and can run around his backhand, he’ll dictate, and win, most rallies. Perhaps Federer watched some of the Hewitt-Nadal semifinal, in which the Australian repeatedly stepped inside the baseline to hit opposite-court forehands, often charging the net (Hewitt’s volleys and savvy at the net are underrated). Nadal lost a set and might have lost the match if Hewitt’s serve was not such a liability.

Federer’s serve has hurt him in recent weeks, too, but it was superb in the second set yesterday. Though he lost his rhythm in the third, the rest of his game was so strong (and Nadal’s, frankly, so weak and marred by tired errors) that it didn’t matter. Federer also took more risks on his service returns, to good effect. Nadal has admitted that he rolls in first serves against Federer — why do anything else when your opponent simply blocks these offerings back over the net? In the Monte Carlo final, Federer treated Nadal’s serves like a polite invitation to start a rally. Yesterday, he took some rude cuts at them, hitting a few winners and seemingly grooving his forehand, which overwhelmed Nadal in the third set.

Just as this victory is good for Federer, the loss, it seems to me, is good for Nadal (perhaps that’s why Nadal’s uncle and coach, Toni, was smiling after the match). “The Streak” won’t be on the line in Paris, and he’ll have the luxury of claiming that Federer is the favorite to win the tournament (Nadal loves to cast himself as an underdog to Federer, but any such attempt would have been laughable had he beaten Federer for a sixth time on clay).

Best of all, now that Federer has shown he can execute a winning strategy, Nadal can adapt to it. If these two meet again in the French Open final, expect Nadal to hit more aggressive first serves and to sneak into the net on occasion, as he did with great success in the first set. Federer might win again, but Nadal is too good to be mesmerized by Federer’s magic a second time.

tperrotta@nysun.com