Sinner served a three-month suspension following a settlement with the World Anti-Doping Agency in February after authorities accepted the anabolic agent clostebol had entered his system inadvertently via massages from his then physiotherapist at Indian Wells in March 2024.
Djokovic said he did not believe Sinner had acted deliberately, but added the controversy over the perceived disparity between Sinner's treatment and that of lesser-known athletes would linger around the Italian, much like his own deportation from Australia in 2022 over his refusal to take a COVID-19 vaccine.
"That cloud will follow him just as the cloud of COVID will follow me, for the rest of his, or my career in this case," Djokovic said in an interview with Piers Morgan.
"It's just something that ... it was so major and when that happens, over time it will fade, but I don't think it will disappear. There's always going to be a certain group of people that will always try to bring that forward."
Djokovic raised questions about the handling of Sinner's case after the 24-year-old was allowed to return to action in May without missing a Grand Slam.
The International Tennis Integrity Agency has remained firm that all its cases are dealt with based on facts and evidence and not a player's name, nationality or ranking.
"There is the lack of transparency, the inconsistency, the convenience (of) the ban coming, between the slams, so he doesn't miss the others - it's just, it was very, very odd," Djokovic added.
"I really don't like how the case was being handled and you could hear so many other players, both male and female, who had some similar situations coming out in the media, and complaining that it was a preferable treatment."
