The sports scientist Stephen Dank is suing the National Rugby League Club Cronulla over allegations he injected players with horse drugs.
The club is currently the subject of an investigation by Australia's Anti-Doping Authority.
Lawyers for Dank say comments made by former Sharks chairman Damian Irvine are defamatory and that the club is legally responsible.
Irvine has since resigned and apologised for the comments.
Dank, a former Cronulla employee, has denied any wrongdoing and is currently a trainer with the NRL club Paramatta.