Novak Djokovic of Serbia returns the ball to Rafael Nadal of Spain during their men's quarter-final match during the French Open tennis tournament at the Roland Garros stadium in Paris, France, June 3, 2015. REUTERS/Jean-Paul Pelissier

By Martyn Herman

LONDON (Reuters) - Coaches will come under nearly as much scrutiny as the players over the next fortnight at Wimbledon with every facial gesture captured on the TV cameras and repeated in super slow motion.

The relationships between the players and those in their box, which in home favorite Andy Murray's case is packed to capacity, makes for fascinating viewing.

But with all forms of on-court coaching prohibited at grand slam tournaments, the line between offering support and passing on coded tactical messages can by blurred.

Men's title-holder Novak Djokovic, who has former champion Boris Becker working as head coach alongside Marian Vajda, was asked at his pre-tournament news conference on Sunday whether Becker pushed the boundaries of what was acceptable -- the insinuation being that instructions were being passed.

"I don't think that we're cheating," the 28-year-old Djokovic, who has worked with the German since 2013, said.

"I don't think that's how you can call it. I mean, there are special ways of, I would say, communication.

"As (Boris) mentioned, the way you look at each other, the way you feel your box, and box feels what you're going through on the court. I think that's something that just gives you that reassurance, gives you that confidence.

"It's not necessary that he tells me where to serve or to which side of the opponent's court I have to play, because that doesn't happen.

"But it's more, you know, encouragement, and more of a support and reassurance in those moments."

With so many cameras following the matches of the top players Djokovic said it would be picked up immediately if a coach was offering specific tactical instruction rather than just psychological support.

But he also said that there were times when the player leaned heavily on his support team.

"We can't pretend like that's not happening in tennis," he said. "Of course, there are situations when it happens, and not just with the top players, with everybody.

"Of course, there are certain rules, but also there are times when the team of the player communicates with the player when he gets to go and take the towel in the corner, which is closer to the box, or, you know, different ways.

"I think it's all fine as long as it's not regular. Also that's up to the chair umpire or supervisor to decide if somebody's breaking the rules or not."

Djokovic, bidding for a third Wimbledon title, will open play on Center Court on Monday with a tricky-looking test against Germany's Philipp Kohlschreiber.

(Reporting by Martyn Herman; editing by Toby Davis)