Serbian tennis star Novak Djokovic, ranked number one in the world, expressed his sadness and said he was "heartbroken" to see former German tennis player Boris Becker in prison.
Djokovic said - during his participation in the French Open tennis - that "My heart breaks with sadness to see him go through this. I am only sad because someone I know well, and I consider him from my family as he is a legend in our sport, he has to live with what he is going through."
Becker coached Djokovic from 2014 to 2016 and together they celebrated many successes.
"We had a great relationship, even after our working relationship ended," Djokovic said.
"I'm in contact with one of his sons, Noah, and asked him if I could do anything to help him. But it's bad. I just hope he stays healthy and strong."
Becker - the winner of six titles in the four Grand Slam tournaments (Grand Slam) - was sentenced to two and a half years in prison last April in connection with bankruptcy cases.
He is currently in a prison in London.