BEIJING, China (AFP) — Top-ranked Jannik Sinner defied the controversy surrounding his doping case to join Carlos Alcaraz and Daniil Medvedev on Monday in the China Open semifinals.

The defending champion will face Chinese wildcard Bu Yunchaokete after defeating Jiri Lehecka 6-2, 7-6 (8/6) for his 14th win in a row.

The 23-year-old is under the microscope anew after the World Anti-Doping Agency (WADA) said on 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) cleared the Italian of wrongdoing in August and allowed him to continue playing, 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.

WADA has appealed the case to the Court of Arbitration for Sport.

“For sure I had sleepless nights during this time. Now again it’s going to be not easy,” he said on Monday, admitting that “this is a very difficult moment.”