Novak Djokovic has called for anti-doping rules in tennis to change in the light of Jannik Sinner’s recent case and he says that he understands why players have questioned whether doping cases are treated equally.

“There is a lot of issues in the system,” Djokovic said. “We see a lack of standardised and clear protocols. I can understand the sentiments of a lot of players that are questioning whether they are treated the same. Hopefully the governing bodies of our sport will be able to learn from this case and have a better approach for the future. Collectively there has to be a change, and I think that’s obvious.”

On Tuesday, Sinner and the International Tennis Integrity Agency (ITIA) announced that the world No1 had failed two anti-doping tests in March before an independent tribunal ruled that the Italian bore no fault or negligence for the presence of the banned substance clostebol after he successfully argued that he had been contaminated by his physio.

Since then, numerous players, including Denis Shapovalov, Lucas Pouille and Britain’s Tara Moore, have argued that top players are subject to different rules compared with lower-ranked players. Moore was out for 19 months during her provisional suspension after testing positive for metabolites of nandrolone and boldenone in 2022 before receiving a ruling of no fault or negligence in December.

“Many players – without naming any of them [as] I’m sure you know already who – have had similar or pretty much the same cases, where they haven’t had the same outcome,” Djokovic said. “And now the question is whether it is a case of the funds, whether a player can afford to pay a significant amount of money for a law firm that would then more efficiently represent his or her case. I don’t know. Is that the case or not? That’s something really I feel like we have to collectively investigate more.”

Carlos Alcaraz responded with caution when asked about his rival’s positive test. “In the end, it’s a very delicate subject,” Alcaraz said in Spanish. “It’s a very, very serious subject. There are things behind the scenes that many people don’t know, certainly that I don’t know. So in the end it’s very difficult, honestly, to talk about the subject. He tested positive, but there must be some reason why they let him continue playing that we don’t know. So I can’t talk much more about the subject either.

“In the end, they’ve declared him innocent and he’s in the tournament. I think there’s not much more to talk about and at least I don’t have much to say. It’s something that is talked about [in the locker room].”