Boris Becker has claimed that Novak Djokovic did not put enough hours into practice during the final six months of the season, which ended with the Serbian losing the number one world ranking to Andy Murray.
Becker has been speaking for the first time since Djokovic dropped the German from his coaching setup following a three-year partnership.
In that time, Djokovic won six Grand Slam titles, but 2016 ended on a disappointing note as he was knocked out in the third round at Wimbledon and later lost in the first round at the Rio Olympics.
The 29-year-old suffered a further blow when he lost to Stanislas Wawrinka in the US Open final and relinquished his place at the top of the world rankings to Murray during the final few tournaments of the year.
While speaking to Sky Sports News, Becker said: "He didn't spend as much time on the practice court in the last six months as he should have and he knows that. Success like this doesn't happen by pushing a button. Success like this doesn't just happen by showing up at a tournament. You have to work your bottom off because the opposition does the same.
"I know the US Open loss in the final against Stan hurt. I think that is what he needed maybe in a funny way was to lose a little bit, to realise what it is like to lose, because he hasn't been losing for two and a half years.
"I am sure the fact that he lost the number one ranking to Andy Murray is going to hurt, but he has got to go back to work. He has to go back to the office and practice these hours and refocus on what made him strong in the first place."
Djokovic, who has 12 Grand Slam crowns to his name, spent 122 weeks as world number one while working with Becker.
