Four-time Grand Slam champion Carlos Alcaraz said Sunday that the steroid case involving Jannik Sinner was "not good" for tennis but sympathised with the world number one.
The World Anti-Doping Agency on Saturday said it had appealed to the Court of Arbitration for Sport after Sinner was cleared of wrongdoing last month.
WADA is seeking a ban of up to two years after the Italian twice tested positive for traces of the banned substance clostebol in March.
The International Tennis Integrity Agency subsequently 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.
Alcaraz, the Spanish world number three, said at the China Open: "I think for tennis it's not really good, not really a good sign for tennis in general."
There has been scepticism among some players about Sinner's explanation for why he failed the two tests, but Alcaraz took a more sympathetic stance.
"It is difficult for him. I know everyone is talking about it, the news is talking about it," he said, having reached the last eight in Beijing.
"Probably as he said before New York (US Open), people started to look at him in a different way.
"I don't know how it can be, but for sure I understand the position. I feel (for) him.
"But anyway, the game and the level that he's playing with everything he's been through right now, it's insane."
Alcaraz added: "I hope that this thing... will be aside soon and he's able to stay focused on what he loves, and that is playing tennis, trying to keep going."
Sinner is also playing in Beijing, where he faces Jiri Lehecka of the Czech Republic on Monday.