Serena Williams has insisted she would have been stripped of grand slam titles and given a 20-year ban had she failed a drugs test in the manner of Jannik Sinner.

Sinner is serving a three-month suspension that expires on May 4 after returning two positive tests for the banned anabolic steroid clostebol last year.

The 23-year-old from Italy, who remains No.1 despite his absence, reached an agreement with the World Anti-Doping Agency after claiming he had been inadvertently contaminated while being massaged by a member of his team.

WADA accepted the current Australian Open and US Open champion "did not intend to cheat" and that the result was due to "negligence of members of his entourage".

Williams, who won 23 grand slam titles in a 27-year professional career, suggests he has been treated leniently.

"Fantastic personality. I love the guy, I love this game. He's great for the sport," she told Time Magazine.

"I've been put down so much, I don't want to bring anyone down. Men's tennis needs him.

"If I did that (tested positive for doping), I would have gotten 20 years. Let's be honest. I would have gotten grand slams taken away from me."