American Jenson Brooksby said it was "unfair and unfortunate" that he had to serve a 13-month ban for missing three drugs tests while two of the world's leading players were handed minor reprimands after testing positive for banned substances.
Brooksby was hit with an 18-month ban in October 2023 for three "whereabouts failures" in a 12-month period but had the suspension reduced to 13 months on appeal at the Court of Arbitration for Sport after disputing the second missed test.
Hampered by injury after his ban ended, he finally made his return to tennis at the Australian Open where he lost 6-2 6-0 6-3 to compatriot Taylor Fritz in the first round on Tuesday.
Brooksby's case contrasts sharply with that of men's world number one Jannik Sinner and women's number two Iga Swiatek, who failed doping tests but saw minimal disruption to their careers.
Sinner lost prize money and ranking points but was allowed to keep playing after his team filed urgent appeals against provisional suspensions, while Swiatek returned to action after a one-month ban.
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The handling of their cases prompted several fellow players to highlight what they said was a two-tier anti-doping system within the sport.
"It's interesting to see ... there's a lot of different cases like Sinner and Swiatek. I can't say I know enough about the details on that," said Brooksby.
"But I do think it's a little strange how there's varying suspension lengths for whether you're testing positive for a substance or like the one I had, where I didn't.
"That's a little unfair and unfortunate. But there's nothing I can do about the system."
The independent International Tennis Integrity Agency maintains that all doping cases are dealt with based on facts and evidence and not a player's name, ranking or nationality.
Sinner faces a ban of up to two years after the World Anti-Doping Agency appealed his case at sport's highest court.
Brooksby sympathised with players who had lost large chunks of their careers while trying to clear their names.
"It's hard. I feel for anyone who's hand any type of issues," the 24-year-old added.
"It's a really tough thing for any player to manage. All you can do is learn and go forward."
Brooksby said every experience was positive on his return to Melbourne Park, the venue of his last match two years ago.
"The players are saying 'hey welcome back, good to see you out here.' There's a lot of positive energy," he said.
"I've missed being on the road and in these atmospheres. It's been great."