When it comes to overstepping the boundaries of proper behavior at the All England Lawn Tennis and Croquet Club, three-time Wimbledon singles champion John McEnroe arguably is without peer. So it's oddly fitting that McEnroe used his perch as an NBC commentator to chastise Australia's Lleyton Hewitt for repeatedly screaming, "Come oooon!" during his quarterfinal against Feliciano Lopez whenever he made a key point or the Spaniard flubbed one.

"I feel it myself when I'm commentating, so you know how annoying it is to Lopez," McEnroe said.

But Hewitt surely will need whatever adrenaline that primal howl gives him when he faces world No. 1 and two-time Wimbledon champion Roger Federer in Friday's men's semifinal.

Hewitt has lost his last seven matches to Federer, who has played nearly flawlessly en route to his third consecutive Wimbledon semifinal. The Swiss holds a 34-match winning streak on grass. And he simply can't imagine the challenge of facing a player who has beaten him seven times in a row, he conceded, because he has few bad records against anyone.

"He's beaten me enough to believe in his chances," Federer said of Hewitt, Wimbledon's 2002 champion. "And on grass I think anything can happen against him. He knows how to win the title here."

Hewitt only recently returned to the game, competing in the Queens' court tuneup two weeks before Wimbledon after missing two months with broken ribs. His play has gotten stronger with each round.

McEnroe was unstinting in his praise following Hewitt's quarterfinal victory over Lopez, who had dismissed Marat Safin and Mario Ancic. Against Lopez, Hewitt committed just 12 unforced errors, served well and returned even better. As usual, he peppered his play with dozens of, "Come oooon's!'"

Hewitt's histrionics didn't bother his third-round opponent, American Justin Gimelstob, who made a point of telling him afterward how much he admired his zeal. Sure, Hewitt's a screamer, Gimelstob conceded. And he doesn't acknowledge compliments from his opponents, like "Nice shot," during matches, much less extend any.

"But here's a guy who's undersized and undermanned [5 feet 11, 170 pounds], playing against great athletes -- not me being one of them -- but the Roger Federer, Andy Roddick, Pete Sampras-type players -- and he just has to figure out a way to try to beat them with the skills he has," Gimelstob said. "I have tremendous respect for the fact that he goes out there and competes on the tennis court."

Asked what he thought of Hewitt's chances against Federer, Lopez smiled and said: "For sure he will get another chance, no? But Roger is another level. It's not me."