Italy Davis Cup winner Sinner 'heartbroken' over doping accusations

World number one Jannik Sinner said his off-court turmoil over doping accusations was "heartbreaking", after winning the Davis Cup with Italy on Sunday to complete a stellar year.

The 23-year-old won the Australian Open, US Open and ATP Finals before starring for Italy as they claimed a second consecutive Davis Cup triumph, but admitted he is not able to play with a completely clear head.

Sinner is still waiting for the outcome of the World Anti-Doping Agency's (Wada) appeal against his initial exoneration for twice testing positive for traces of the steroid clostebol in March.

"Of course it's in the head a little bit," said Sinner.

"The most important part is all the people who are around me, who know me as a human being trust me -- that's also why I kept playing the level I have.

"Those who know me, I was emotionally a bit down, a bit heartbroken. Sometimes life gives you difficulties and you just have to (deal with) it."

After Italy defeated the Netherlands in the final, Dutch captain Paul Haarhuis said from the outside the doping case against Sinner was impossible to analyse.

"About doping, we never know what happened," said Haarhuis.

"What's my feeling? Jannik is an unbelievable nice guy, a great player, but we never know what happened."

Sinner previously told the International Tennis Integrity Agency (ITIA) that small quantities of clostebol found in his system were due to "contamination by a member of his staff who had applied an over-the-counter spray containing clostebol on his own hand to treat a small wound".

The ITIA accepted Sinner's claim and he escaped a lengthy ban, but Wada appealed and is demanding a suspension of one to two years.

Sinner became the first player since 20-time Grand Slam winning Swiss great Roger Federer in 2005 to go through a season without a defeat in straight sets.

The Italian defeated Netherlands' Tallon Griekspoor in the second singles rubber to clinch the Davis Cup, after Matteo Berrettini beat Botic van de Zandschulp in the opener.

"Coming back as defending champions and winning again is one of the best feelings," said Sinner.