Novak Djokovic says he is “heartbroken” for his former coach Boris Becker, who was jailed on Friday for hiding assets.
Djokovic also worries whether Becker will be able to lead a “normal” life when he is released from prison.
Becker, 54, coached the Serb for three years, beginning in December 2013.
Speaking in Spain ahead of the Madrid Open, Djokovic said: “He’s a friend, a long-time friend, a coach for three, four years, someone I consider close in my life and has contributed a lot to my success in my career.”
Djokovic declined to comment on the court case, but added: “I just pray for him. I hope things will be well in terms of his health, his mental health, because that’s going to be the most challenging part.
“I just hope he will go through this period that he has to be in jail and that when he comes out he’s, you know, being able to live his life as, I don’t know if we’ll use the word ‘normal’…”
Boris Becker’s daughter, meanwhile, has shared her “shock” over her father’s prison sentence, adding she fears it will be hard on his young son.
Anna Ermakova said she had written to the judge who jailed her tennis champion father for two-and-a-half years for bankruptcy fraud.
She added she had asked for leniency due to his 12-year-old son, Amadeus, now being “without a father figure”.
Ms Ermakova, who was conceived during Becker’s infamous sexual encounter with waitress Angela Ermakova at London restaurant Nobu in 1999, told German newspaper Bild: “I wrote a letter to the court to express my concern for my little half-brother, Amadeus.
“After all, he is only 12 and will now have to do without a father figure, whom he will lack during a difficult phase of his development.
“It’s not fair to him. It’s going to be tough for Amadeus.”
Judge Deborah Taylor gave the six-time Grand Slam champion a 30-month sentence at Southwark Crown Court on Friday, for hiding £2.5m of assets and loans to avoid paying his debts.
He will serve half of the sentence.
The 54-year-old three-time Wimbledon champion and former world number one was declared bankrupt on 21 June 2017 due to owing creditors almost £50m over an unpaid loan of more than £3m on his estate in Majorca, Spain.
BBC commentator Becker transferred almost €427,000 (around £390,000) from his business account to others, including those of his ex-wife Barbara Feltus and estranged wife Sharlely “Lilly” Becker.
The father-of-four also failed to declare his share in a £1m property in his home town of Leimen, Germany, hid an €825,000 (almost £700,000) bank loan, which was worth £1.1m with interest, and concealed 75,000 shares in a tech firm, valued at £66,000.
Becker, who was handed a two-year suspended sentence for tax evasion and attempted tax evasion worth €1.7m (around £1.4m) in Germany in 2002, was found guilty last month of four offences under the Insolvency Act between 21 June and 3 October 2017.
‘I will support him’
Ms Ermakova told Bild: “I will support him and I will visit him whenever I can.
“I hope that will help him a little to get through the time.”
Becker has two sons, Noah, 27, and Elias, 22, with his first wife, Ms Feltus, as well as Amadeus with his second wife, Dutch model Lilly Kerssenberg.