When he was growing up in Switzerland, Roger Federer did not pay much attention to a young American tennis player with long locks, denim shorts, and a deadly forehand. Andre Agassi could spank the ball with the best of them and his popularity was second to none, but the budding Swiss star had a different kind of game in mind for himself.

“I was more about Sampras, Becker, or Edberg,” Federer said. “I didn’t follow his career as closely as the other players.”

Federer, 23, has emulated much of what those serve and volley champions brought to tennis, though he charges the net a little less often and performs better than his idols from the baseline. Tonight, he’ll put everything he has on display against Agassi, 34, in the most anticipated match of the tournament.

Meetings like this give tennis the allure of championship boxing, and in this quarterfinal fight of contrasting styles, Federer, the young buck with a killer right hand, is the favorite against a patient tactician seeking his ninth Grand Slam title. The two have met six times before. Agassi won the first three, from 1998 to 2002, and Federer the last three. In their only meeting this year, in March, Federer won two sets to one in a semifinal at a hard court tournament in California.

“There’s nothing more you can ask for than to play a big event against the best player in this environment,” Agassi said. “It’s time to bring the best tennis.”

So far in this tournament, Federer has been far from his best. He’s made more than 30 unforced errors in each of his matches and has already lost his serve five times. Against unseeded Marcos Baghdatis of Cypress, Federer was broken twice and dropped a set in a tiebreak. And he may be rusty tonight, since he didn’t have to play his last round because of an injury to his opponent.

Federer’s erratic play could be an aberration, but it’s worth noting that he suffered early defeats in his two tournaments leading up to the Open, Cincinnati and the Olympics. Federer, who won two Grand Slams this year, has been traveling without a coach the entire season, and for the first time is showing that he might need a few words of advice.

Nonetheless, he said he has every intention of bringing something extra to the court tonight for what amounts to the biggest evening match he has ever played in New York.

“The good players usually come up with some good stuff when it’s important,” he said. “In the past I’ve done it. That’s what has to happen again against Andre.”

Agassi will have a good chance if he can serve well and steer the ball away from the top seed’s dangerous forehand.

“I think his biggest weapons are his forehand and his movement,” Agassi said. “He’s a really explosive mover. His forehand’s just a nasty shot. He does a lot of things really well. He does a few things great.”

A key indicator of Agassi’s performance will be his first serve. If Agassi only puts around 55% of his first serves in the box, he’ll feel pressure from Federer early and often. But if he can keep his percentage up around 65% or even 70%, as he did in his last two matches, Agassi should be able to hang in there and dictate more of the points. Otherwise, his chances will diminish.

One thing’s for certain: Agassi will have the crowd behind him.

“I’m going to try to give the crowd something to cheer about,” he said.