Defending champion Novak Djokovic's past glories at Wimbledon will count for little when the 2015 tournament begins next week, according to his coach Boris Becker.

Djokovic triumphed at the All England Club for the second time last year when he overcame seven-time winner Roger Federer in five sets.

The Serb has been in stunning form in 2015 to retain the world number one spot, though his defeat in the French Open final to Stan Wawrinka showed he was not unbeatable.

And Becker, a three-time Wimbledon champion himself, expects his protege to face a difficult challenge in keeping hold of his title - with home favourite Andy Murray, who won at Queen's Club on Sunday, among the biggest challengers.

"Well I'm coaching Novak Djokovic, so he's the current Wimbledon champion, we had a spectacular run last year, but it all starts from scratch again now, first round will be first round for everybody, so it'll be a very tough tournament," said the German.

"I like Andy, we have a good relationship, obviously I'm coaching his toughest rival so we have to keep it very professional.

"But I've known him for many years, he's in great form, he's the four-time Queen's Open champion now, one of the favourites for Wimbledon, but obviously I'm in Novak's corner, so I have to support."