WIMBLEDON, England — Like a blue streak, they scamper across the green grass of Wimbledon as fast as they can, gobbling up tennis balls one after another.

They also stand at attention, hands behind their backs, in the corners of the court, patiently waiting for a player to beckon for a towel.

The "they" are the ball boys and ball girls at the All England Club, the ones in the blue Ralph Lauren shirts and shorts (and hats) who keep Wimbledon matches flowing by chasing down all those fluorescent yellow Slazengers so the players can get back to work as quickly as possible.

"You're constantly running for the whole hour," said Michal Saladziak, a 15-year-old ball boy from London working at Wimbledon for the second year in a row. "It can get quite difficult."

The ball kids, about 250 of them separated into 42 teams of six at this year's tournament, go through a grueling process for selection — first at their schools and later by the club. And then there's the training, making sure they are fit enough to take one-hour turns on a court.

The hope, of course, is that they won't make any mistakes.

"We're very much in the background," said Sarah Goldson, the director of the ball boys and ball girls at Wimbledon. "We hope that people don't notice us."

They certainly are noticeable, though. Almost every bad serve sends one of them scurrying somewhere. Almost every change of service sees them rolling those felt-covered orbs from one end of the court to the other. And almost every stoppage sees one reaching for a towel to hand over to a sweaty player.

It's work, for sure. But it's a job lots of kids wish they could get, even if there are some small drawbacks.

"Some of my friends didn't make it," said Ben Couzens, a 15-year-old ball boy from Surrey who is new to the tournament this year. "We're not allowed to talk (on court), which was the hardest part for me. Can't let your concentration down."

Besides training for fitness, the kids who make the cut — approximately half of them are girls — also have to pass a test of tennis knowledge. Knowing that players get two serves per point, or more if one hits the net and still lands in, is important because the ball kids need to be ready to toss over replacements.

They also need to know what to do when things go awry.

"We've been told to take initiative," Saladziak said. "If something unexpected happens, you just have to react to it."

The average age for the ball boys and ball girls is 15, and they are tennis fans, too, so seeing their favourite players up close is definitely one of the highlights.

Katie Compton, a 15-year-old ball girl from London, is eagerly anticipating the moment when he she encounters eight-time Wimbledon champion Roger Federer.

"I'm still waiting to get a glimpse," said Compton, who is back at Wimbledon for the second time. "I haven't seen him yet, but hopefully."

Federer surely knows what she is going through. He was a ball boy as a kid growing up in Switzerland at the Swiss Indoors in his hometown of Basel.

"I remember being in their shoes and me walking out (for the trophy ceremony) with my friends at the time. I did it for two years," Federer said late last year in an interview with the men's ATP Tour after winning his ninth title at the event. "Then I give them all a medal, thank them for their efforts. I feel like I'm looking at myself in some ways."

The ball kids at Wimbledon who spoke to The Associated Press didn't have any horror stories about rude players. Or maybe they were just too shy to mention anything.

"Some people are nicer," Couzens said, "depending on whether they're winning or losing."

Not all the ball kids at Wimbledon get the opportunity to toil on the soil of the biggest courts, however. Goldson said there are six teams that work Centre Court and No. 1 Court, the two biggest stadiums on the grounds. And all the ball boys and ball girls are assessed constantly throughout the fortnight.

The dream, though, is obvious.

"The ultimate goal," Saladziak said, before Couzens finished his sentence, "is to do the final."

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