What exactly is wrong with Murray? Becker, McEnroe try to find out...

'I cannot remember a time when the number one went through such a phase. Maybe a bad week, a bad month, but for Andy it's been pretty much the whole year.'

Andy Murray's wretched form ahead of the next week's French Open has left pundits including Boris Becker scratching their heads about what exactly is wrong with the world number one.

A year after the Briton produced a stunning claycourt season, winning the Rome title and reaching the final at Roland Garros for the first time, he is struggling to locate his A game ahead of his most important part of the season.

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Wimbledon champion Murray, who de-throned Novak Djokovic as the world's top-ranked player last November during a run of 24 consecutive match wins, has won only one title in 2017 and admits he has struggled with motivation.

Six-times major winner Becker, the former coach of Djokovic, has kept a close eye on Murray's season and is mystified about what has gone wrong for the 30-year-old.

"I don't know what's happening with Andy right now. He was so good last year and the year before," Becker said in an interview to be screened by Eurosport.

"This year, apart from Dubai, he was not close to playing at the level he was last year. I like Andy, I like his coaching staff, we speak a lot. But what I see on the court, I don't like. I don't know what's going on with him.

"I cannot remember a time when the number one went through such a phase. Maybe a bad week, a bad month, but for Andy it's been pretty much the whole year."

A bout of shingles and an elbow injury have not helped Murray's season which reached new depths in the last couple of weeks with dispiriting defeats by Borna Coric and Fabio Fognini in Madrid and Rome respectively.

Becker believes he will be vulnerable at the French Open, especially in the early rounds.

"I hope he goes to the second week. He needs a couple of wins to get his confidence back," the German said.

"I don't think he's one of the favourites and I think he should just concentrate on getting to that second week and have at the back of his mind the grass court season.

"But another early loss, this time at the French Open, would not be good for him."

One of Becker's old adversaries John McEnroe is less surprised by Murray's dip, saying he is suffering the effects of a monumental 2016 when he won Wimbledon, the Olympics and reeled in Djokovic in the rankings.

"Andy had to put so much effort into finishing world number one last year that he expended so much energy to get there," McEnroe told Reuters. "It was an amazing achievement.

"He's having trouble keeping up that energy which is necessary. It's extremely hard.

"I don't know if he has some nagging injuries but perhaps he lost some motivation when he reached world number one."

Brad Gilbert, who helped Murray crack the top 10 in 2007, said his former charge will fight back.

"He owned a lot of guys last year but you start losing a bit and guys start to have some belief against you," Gilbert said during a conference call.

"He is struggling but now is as good a time as any to turn things around. The fact that (Roger) Federer and (Rafael) Nadal are back (winning the big titles again) will inspire Andy and put a little fuel in the fire."