World number one Jannik Sinner said on Monday that he was in "a very difficult moment" and enduring sleepless nights over his doping case.
The 23-year-old is under the microscope anew after the World Anti-Doping Agency (WADA) said Saturday it was seeking a ban of up to two years after he twice tested positive for traces of the steroid clostebol in March.
The International Tennis Integrity Agency (ITIA) had cleared the Italian of wrongdoing in August, and weeks later he won the US Open for his second major title.
The ITIA accepted Sinner's explanation that the drug entered his system when his physiotherapist used a spray containing it to treat a cut, then provided massage and sports therapy to the player. "First of all it's not a situation where I like to be in, it's a very delicate and difficult and also different situation," Sinner said in Beijing after defeating Jiri Lehecka in the quarter-finals 6-2, 7-6 (8/6). "But what I know is that I always try to remind myself that I haven't done anything wrong. "For sure I had sleepless nights during this time.