Hawthorn defender Tim Mohr suffered a dislocated knee in a practice match for Box Hill on Sunday.
Mohr was taken with the Hawks’ third pick in the 2018 rookie draft after a 48-game career with GWS.
GM-Football Graham Wright said it was disappointing news for Mohr and the club.
“It’s always disappointing for any player to suffer a serious injury so early in the season,” Wright said.
“Tim was taken to hospital having dislocated his knee and will stay in overnight for observation.
“The specialist will assess him and we will provide a further update following this.”