NEW YORK: It is a question that is asked of tennis players in almost every news conference; “What were you thinking when?”

As in every sport, tennis players constantly strive to be “in the zone”, that state of mind when everything goes perfectly without any conscious thought.

Most players truly get in the zone only a handful of times a year. Otherwise, they have to cope with the wanderings of the mind that can affect focus and at worst, lose them matches.

While amateurs might find themselves thinking bizarre thoughts like: “did I leave the oven on?” or “what will I tell my friends if I lose this?”, professionals are better at staying in the moment.

But there is still the odd time where the mind goes AWOL and then anything goes, as Roger Federer explained a few years ago.

“Sometimes if you have a song in your mind, sometimes you're thinking of what's going to happen tomorrow, what's the plan for tonight,” he said.

“All those things happen. We're human at the end of the day. We're not a machine and go from like point to point like RoboCop. I have to remind myself to focus.”

Balancing being concentrated with being relaxed is not easy but professionals play so many matches that they improve with age.

For juniors, who do not have that bulk of experience under their belt, it can be even more difficult to stay in the moment.

“When I usually have lapses it's when I have been listening to music,” said Francis Tiafoe, a 16-year-old American, considered to be one of his country's biggest hopes.

“If I'm winning easy, say by a set and a break, I might start singing a few lyrics.

“And then for a couple of shots, I'm like: 'what's going on? Then I'm like: 'OK, here we go and I am back.”

UNUSUAL SITUATION

South Africa's Raven Klaasen, who reached the doubles quarter-finals in New York with Eric Butorac and made the Australian Open final in January, said it was unusual for professionals to lose their way for long.

“It's also a bit easier in doubles,” he said. “I think that only happens when I'm a bit cold, if I haven't won a point on one side for a while.

“The good thing in doubles is that your partner can help snap you out of it.

“But in juniors your partner can be your worst enemy, sometimes - if they're not focused then your mind can start drifting.”

For some players, staying focused is more of a problem than others.

“Sometime if I'm fed upit's like, I don't care,” said France's Gael Monfils, who takes on Federer in the quarter-finals of the US Open on Thursday night.

“It's like, OK, next one. It sounds bad in English, but what I mean is, care about the match, I don't care about other things.”

Occasionally, a player's mind can fail them even when they are 100 percent focused, as happened to Andy Murray on match point in the 2012 U.S. Open final when he lined up to the wrong side of the court.

“I just think it was all to do with being so much in the zone, and while I haven't done it too much, I watch a lot of matches and it does happen to other players,” the Scot said in a column for The Australian a few months later, admitting he was a little embarrassed at his mistake.