Serena Williams said she screamed and jumped after a referee's decision that denied the United States a goal against Slovenia.
Wimbledon's defending champions are not alone in fervently supporting their national teams in South Africa. On the groomed grounds of the All England Club, the tennis elite debate World Cup tactics, talk up and tease each other about their favorites.
One hitting partner drew a smile from Serbian player Novak Djokovic when he said Serbia was lucky to beat Germany, one of the World Cup favorites.
On the grass practice courts Sunday, Rafael Nadal, who pursued tennis over football at an early age, flipped a tennis ball into the air with a flick of his left foot, then kicked it high with his heel. Kim Clijsters showed less flashy footwork, bouncing a ball a couple of times before it sailed off her toes into the fence.
The library-like surroundings of Wimbledon are far, in mileage and atmosphere, from the scrappy shotmaking on the field and din of vuvuzelas, or plastic horns, in the stands of South African stadiums.
Wimbledon has banned vuvuzelas at the championships this year, and World Cup games will not be broadcast on the big screens or scoreboards on the Wimbledon grounds.
Federer, also a football player when he was younger, said he didn't get in touch with Spaniard Nadal after Switzerland's unexpected 1-0 victory over Spain.
"I'm not the type of person who rubs it in," said Federer, who had spoken to the Swiss football team about pressure and handling the media before the World Cup, at the request of the coach.
"We know the bad times can come by very quickly.But obviously, after a match like this, you're allowed also to start dreaming that you could go much further in the competition."
Federer starts his match against Alejandro Falla of Colombia at on Monday, two hours before Switzerland's World Cup contest with Chile.
"Maybe I can install a little screen on Centre Court on the change of ends," he said, smiling. "It's happened in the past that I've had to play matches during important things in my life. You know, kind of went on court last year many times thinking that Mirka was going to give birth to my children.
That was a bit more, you know, crazy than Switzerland playing at 3 p.m."
For his part, Nadal said Spain's loss was "very bad luck" and he offered some technical analysis of World Cup play.
"A lot of teams are playing very defensive and it's difficult to play against this kind of team," he said Saturday. "You see, all the matches are very close, 1-0, 0-0.
Germany won the first one, 4-0. And Argentina, I saw two days ago playing well."
World Cup football has traditionally struggled to excite Americans, who stick to baseball, basketball and other staples. Count Serena Williams as an exception. She was incensed when the referee disallowed a U.S. goal in a 2-2 draw with Slovenia on Friday.
"Man, my heart skipped several beats. I'm surprised I'm here. There's no way we shouldn't have won that match. It was really, really upsetting," she said at Wimbledon. "A tie is OK, but we totally got that win. I was really upset about that. But, you know, review."
No stranger to high expectations, Andy Murray, a Scot, said he felt for England's footballers, who are struggling in South Africa and have endured scathing reviews from British media. England drew its matches against the U.S. and Algeria, and face possible elimination.
"Everybody's been there and done it, you know, made bad mistakes. In tennis, you make mistakes at important points in matches, you know, on the biggest stages in the world," said Murray, who has faltered since reaching the Australian Open final in January.
"You just understand that it can happen to everyone."
Sport, Murray said, is a "pretty tough world."
American Andy Roddick, runner-up in an epic final at Wimbledon last year, shared the same sense of outrage as Williams after the controversial US-Slovenia game. He didn't watch the ensuing England game, knowing Londoners would be glued to televisions.
"I decided to take advantage of no traffic and go into the city and have some dinner," Roddick said. "You'd be amazed how quickly you can get down there when an England game is on."