By Steven Wine
The Associated Press

WIMBLEDON, England - Roger Federer shares with Pete Sampras more than just a dominant serve, fearsome forehand, stylish flair and love of grass.

There's also the impassive demeanor and reluctance to show emotion, so that the occasional "Come on!" from Federer when he wins a pivotal point seems startling.

"All in all, I'm very quiet, very calm also from the inside," he said. "Obviously now the way it's going, I don't have any reason to be too nervous."

The way it's going, Federer will be tough to beat in the final two rounds at Wimbledon. The 2003 champion will play Sebastien Grosjean in the semifinals today, and the other match will be between Andy Roddick and Mario Ancic.

Federer lost his serve and a set for the first time in the tournament Wednesday but still beat 2002 champ Lleyton Hewitt in four sets.

Federer earned his first Grand Slam championship a year ago at the All England Club, then added the Australian Open title in February. He's ranked No. 1 and gaining momentum on grass, where he's 22-0 in the past two years.

That doesn't make him a lock for the trophy. Federer and the No. 2-seeded Roddick are on schedule to meet in a much-anticipated final.

Ancic finds himself advancing beyond the fourth round of a Grand Slam event for the first time at age 20.

He's the only change in the final four lineup from last year, supplanting the injured David Nalbandian.

The unseeded Ancic was the last player to beat Federer on grass, pulling off a first-round upset at Wimbledon in 2002.

In Wednesday's quarterfinals, the 6-foot-5 youngster used big serves and emphatic returns to beat Englishman Tim Henman.

The No. 10-seeded Grosjean, a Frenchman who lives in Florida, lost to Mark Philippoussis in last year's semifinals. He's 2-1 against Federer, but those matches all came in 2001.

Reigning U.S. Open champion Roddick is the most imposing potential remaining obstacle for Federer.

They met in the semifinals last year, and Federer won in straight sets, but Roddick has since developed a more well-rounded game.

And the American's formidable serve is better than ever.

He set a Wimbledon record with a 146-mph serve in his quarterfinal victory over Sjeng Schalken and he hit second serves at up to 130 mph.

Still, Roddick is all about power, while Federer is all about variety. Former top players rank Federer's forehand and volley as perhaps the best in the game, and while his serve is slower than Roddick's, he can mix and place it with uncanny consistency.