MELBOURNE, Australia — It was only a year ago that Fernando Gonzalez had little motivation to pick up a racket, never mind play perfect tennis for days at a time. His occasionally brilliant performances, and more frequent terrible ones, sustained a top 25 ranking for five years but eventually damaged his confidence. His backhand was awful, he had trouble returning serve, and he had no inclination to venture to the net. At the Australian Open of 2006, he lost in the first round.

This year in Melbourne, Gonzalez is no longer the free-swinging wildcard who plays with all the subtlety of a jackhammer. He has transformed himself into a consistent contender, most recently at the expense of Rafael Nadal, the no. 2 seed, 6–2, 6–4, 6–3. Nadal played through an injury to what he described as his “famous ass” Wednesday evening, but even if his left leg had been at full strength, the Spaniard would have been hard-pressed to win. No one is playing better tennis at this tournament than Gonzalez, not even Roger Federer. Against Nadal, he served spot on, sliced his backhand low and deep, and worried more about where his fearsome forehands landed, rather than how fast they traveled. On one point, Gonzalez retrieved a ball hit over his head, spun around, and ripped a winner into the corner. Nadal was never in the match.

“I never play three matches in a row at this level,” Gonzalez, who lost in his three previous visits to quarterfinals at Grand Slam events, said.

Gonzalez might not have come this far if not for Larry Stefanki, the former coach of Tim Henman, Yevgeny Kafelnikov, John McEnroe, and, perhaps most important, fellow Chilean Marcelo Rios, the former world no. 1. When Gonzalez called Stefanki last April, he barely knew him.

“I said, ‘Fernando, I’ve said hi to you twice in the locker room, why would you just call me?'” Stefanki said. “I was with Marcelo, I know their culture, been down there quite a bit. Maybe that made him a little more comfortable, that I’d worked with a Chilean before.”

The two worked together for two months before Stefanki signed on fulltime, with simple goals in mind: improve Gonzalez’s return of serve, develop his defense and quickness, and reconstruct his backhand. Gonzalez watched video, lost 12 pounds, and worked on his technique. Stefanki told him he would need to learn patience if he wanted to overcome his reputation as a “one-day wonder.”

“He gets very excited,” Stefanki said. “I’ve tried to tell him not to get like that … not every single big forehand, go ‘Vamos!’ and kind of lose your plan. He’s much calmer now.

“He had beaten everybody one day,” Stefanki added. “I said, ‘Top players do not do that. When you walk out on the court, it’s time to win.'”

Gonzalez struggled in the second round against Juan Martin Del Potro, a match marred by overly aggressive shots and unforced errors from both players (Gonzalez had 42 in the first three sets). Stefanki feared Gonzalez had reverted to his old self, but he has played controlled, and remarkably clean, tennis since. For the tournament, Gonzalez has hit 265 winners and made only 127 errors.

“He doesn’t need to play great every shot to win tennis matches,” Stefanki said.

Before Gonzalez tamed his power against Nadal, Tommy Haas did battle with some personal demons and his least favorite opponent on tour, the no. 3 seed Nikolay Davydenko.

When watching Haas play Davydenko, you should understand German, or in the case of this columnist, stay close to people who do. Davydenko, he of the robotic strokes and tireless legs, can disturb the most stoic opponent. He drives the volatile Haas mad.

Davydenko was at it again Wednesday afternoon in Melbourne, slapping backhands and scurrying about as Haas tried to convince himself that he could break down the Russian’s defenses. Here’s an excerpt from one of his pep talks in between games: “You can’t win like that. Too many errors. Not going to the net. Why do I pay all these people? You are a bloody idiot. But you will win. Fight, fight.” Davydenko, who speaks imperfect English, said afterward, “I think Haas coming crazy.”

Haas did fight, though. For the first time in his career against Davydenko, he won. At the French Open two years ago, he had control of the first set against the Russian in the third round, but he squandered it and gave away the next two sets at love. At the U.S. Open last year, Haas won the first two sets of their quarterfinal match, but lost the next three. Haas compared Davydenko to a ball machine and quipped, “I lost to him, but then again, he doesn’t have a life.” That was two months before Davydenko, who plays more tournaments than anyone on tour, practiced on his wedding day — and delayed his honeymoon — to prepare for the Davis Cup final.

On Wednesday it looked as if Haas would absorb his most devastating defeat yet. He had climbed back from a break of serve in the fifth set, only to face match point, after a double fault at 30–30, on his serve with the score 5–4 for Davydenko. Haas missed his first serve and rolled in his second. The normally dependable Davydenko dumped a backhand into the net. Haas held serve, broke, and held again to seal the match, 6–3, 2–6, 1–6, 6–1, 7–5. He even kept his nerve after losing a match point on an instant replay overrule.

“I wanted the revenge badly,” Haas said, adding that it took him “weeks” to recover from the U.S. Open loss.

This is Haas’s third semifinal appearance at the Australian Open, and the first since he returned from two shoulder surgeries that cost him the entire 2003 season. The previous two times, he lost to Russians: Yevgeny Kafelnikov and Marat Safin. The Safin loss was particularly painful, as Haas led two-sets-to-one before a 50-minute rain delay. Back in the locker room, he lay down for 20 minutes, and when he got up his legs were tight.

“If I would have lost the quarterfinal here against another Russian, it would have been really like, ‘Never going back there again,'” he said.

tperrotta@nysun.com