MELBOURNE, Australia — At age 20, Rafael Nadal has already earned himself a place in tennis history. He has played two French Opens and won them both, while winning a record 62 consecutive matches on clay. He’s won several titles on hard courts, too, and most surprising of all, he reached the Wimbledon final last year in only his third visit to the All England Club. In the rankings, Nadal is a distant second behind world no. 1 Roger Federer, but he has a comfortable lead on everyone else.

Yet as the Australian Open begins, Nadal still finds himself in the position of having to prove that he can win consistently on faster surfaces. There’s good reason why. For Nadal, 2006 can be divided into two parts: before Wimbledon and after. Through the Wimbledon final, which he lost to Federer in four sets, Nadal’s record was 42–5, with five titles, three of them over Federer. After Wimbledon, his record was 14–7, and he didn’t win a title or reach a final. Before, Nadal was indomitable. Afterward, he was a tad better than ordinary. He played Federer once more, in the semifinals of the Masters Cup, and lost in straight sets.

Losing seven matches in the summer and fall is hardly cause for alarm, but it’s the manner in which Nadal lost most of these matches that should concern those who hope he can eventually win major titles besides the French Open. Three opponents come to mind: Mikhail Youzhny (U.S. Open, quarterfinals), Tomas Berdych (Madrid Masters, quarterfinals), and James Blake (Masters Cup, round robin). The pattern was similar in all three matches: Nadal, the best defender in tennis, played deep behind the baseline, hit too many short balls, and proved incapable of weathering a barrage of forceful groundstrokes from his opponents.

Nadal has often talked about playing more aggressive tennis — moving closer to the baseline, losing some of the loop on his forehand, and exchanging a smidgen of service percentage for more power (and if done well, more free points). He could very well succeed in this endeavor, as his performance at Wimbledon last year attests.

His technique and habits, however, put him at a disadvantage when it comes to offense. On his forehand, Nadal uses an extreme grip, takes a long backswing, swings from very low to very high (rather than through), and usually does so while falling backward. While this works nicely on slow clay courts, it’s not a forehand worth imitating, nor is it ideal for hitting the ball early in its bounce. Nadal’s opponents increasingly seek to put him on the defensive early in rallies, and he has trouble regaining control of points once they do.

Federer, speaking to reporters this weekend, said he expected Nadal to adjust in the next few years, in part to lessen the strain on his body. But it won’t be easy.

“He’s still got time to really work on his game, try to come in more, try to improve his slice, try to improve his backhand,” Federer said. “The only question is, ‘Is that going to make him have more success?’ Because in the end, it’s your base that’s going to make you win most of the matches.”

Two years ago, Nadal had a fine run in Melbourne when he lost to Lleyton Hewitt, the eventual finalist, in the fourth round. That performance, before he had won his first French Open, left the impression that Nadal was suited for the Australian Open’s Rebound Ace courts, which are rubbery and contain a little more grit than those at the U.S. Open (the result is a “slower” court — the surface grips the ball more, redirected more of its energy upward for a higher bounce, which gives players more time to collect their thoughts and chase down shots). How slow are the courts? Tennis Australia treats that information like a state secret, but Rod Cross, the physics professor who is hired to calculate the speed every year, said they are “fractionally” faster than last year (Hewitt routinely complains that the courts are too slow).

“On the grand scale of things, it’s not going to make a huge difference,” Cross said in a telephone interview from his office in Sydney.

Nadal has a challenging draw. He first plays Robert Kendrick, the American serve-and-volleyer who nearly defeated him in the second round of Wimbledon. The third round might bring Julien Benneteau or Stanislas Wawrinka, both dangerous opponents. James Blake or Hewitt might follow in the quarterfinals.

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As Nadal looks to build a reputation as an all-around champion, the rest of the men’s field has a decidedly more modest goal: Prove that they are something more than Federer’s chumps. The graceful world no. 1 is always a pleasure to watch, but the consistency and severity of his drubbings leave most of his opponents drooling over his formidable game. That’s fine for fans, but for players, it’s too much. More men need to play with confidence against Federer to make this tournament, and the season, a success.

On the women’s side, don’t be surprised if Kim Clijsters, playing her last year on the tour at age 23, wins her first Australian Open. The Belgian is quite popular here, perhaps more so than the local to whom she was once engaged (Hewitt). Amelie Mauresmo, last year’s winner, had a slow start in Sydney last week, and Justine Henin-Hardenne, who quit in the middle of last year’s final, will miss the tournament because of the breakup of her marriage. Venus Williams is injured; Serena Williams is still overweight. Maria Sharapova should have a strong tournament and could meet Clijsters in the semifinals. Jelena Jankovic won her first tournament of the year and seems intent on becoming more than the erratic player who in 2006 was by turns fantastic (U.S. Open semifinal) and fantastically bad (10 consecutive losses). We leave you with one unheralded woman to watch closely: Anna Chakvetadze, a 19-year-old from Moscow who jumped from no. 33 to no. 13 in the rankings last season.

tperrotta@nysun.com