'Breaks my heart' to see Becker in prison: Djokovic

World number one Novak Djokovic said it "breaks my heart" to see former tennis player Boris Becker in prison, reported dpa.

"It breaks my heart to see him go through this," Djokovic said at the French Open in Paris. "I'm just sad that someone I know so well, who I call part of my family and who is a legend of our sport, has to go through what he's going through."

Becker was Djokovic's coach from 2014 to 2016 and together they celebrated numerous successes.

"We had a great relationship, also in the time after we worked together," Djokovic said.

"I have been in touch with one of his sons, Noah, and asking if there is something that I could do to help. But it's terrible. I just hope that he will stay healthy and strong."

Six-time Grand Slam champion Becker was sentenced to two and a half years in prison last month for bankruptcy offences. He's currently at a prison in London.