HAWTHORN defender Tim Mohr was rushed to hospital on Sunday with a dislocated knee sustained in a VFL practice match.
Mohr, taken by the Hawks in last year's NAB AFL Rookie Draft, suffered the injury in the early stages of Box Hill's loss to the Casey Demons.
The match was stopped for around 45 minutes as an ambulance made its way onto the field to collect the former Giant.
The 30-year-old will spend the night in hospital and undergo scans on Monday to determine any further damage.
"It’s always disappointing for any player to suffer a serious injury so early in the season," Hawks GM of football Graham Wright said.
"Tim was taken to hospital having dislocated his knee and will stay in overnight for observation.
"He will see a specialist in the coming days and we will provide a further update following this."
Mohr debuted for Greater Western Sydney in 2012 before going on to play 48 games in seven years, including two last season before he was delisted.
During an injury-plagued tenure in the harbour city, Mohr ruptured his left ACL in back-to-back seasons in 2014-2015.
He also battled various foot and hamstring injuries.
He arrived at Waverley Park this off-season as defensive cover for James Frawley, Ben Stratton, Kaiden Brand and David Mirra.