Rising Waratahs centre Henry O'Donnell is serving an 18-month suspension for violating anti-doping rules, the club revealed on Saturday.
The 23-year-old played 12 games for the Super Rugby side in 2025 after moving from Western Force. He has also featured for the Junior Wallabies.
But he was absent this season, with the Waratahs saying his period of ineligibility began in July last year.
O'Donnell was sanctioned after testing positive for D-amphetamine and Ritalinic Acid.
The substances are associated with Attention Deficit Hyperactivity Disorder medication and he did not have an exemption at the time.
The Waratahs and Rugby Australia are standing by O'Donnell, noting that Sport Integrity Australia found that the violation was not intentional and not related to sport performance.
"Henry made an error of judgement and has paid a heavy price for that misstep," Waratahs director of performance Barrie-Jon Mather said.
"The club has supported Henry throughout the process and we look forward to his return."
O'Donnell now holds the necessary therapeutic use exemption and will be eligible to return on 1 January next year.