GWS forward Bobby Hill will undergo surgery on Tuesday after being diagnosed with testicular cancer.
The 22-year-old kicked one goal in his team's loss to Brisbane on Saturday and has featured in every game for the Giants so far this AFL season.
But he is now set for an indefinite period out of action.
Medical assessment following his recovery from surgery will determine if any further treatment is required.
"Bobby and his family have our full support, as always, as they go through this period," GWS football manager Jason McCartney said in a club statement.
"His health and wellbeing is our absolute priority and he'll have the best medical care as he undergoes surgery on Tuesday and beyond.
"There'll be a period of time for him to recover before further medical assessment to understand if any additional steps are required.
"Bobby is in good spirits and knows he has the support and love of the entire Giants family."
Hill requested a trade to Essendon at the end of last year, citing family reasons, but was denied the move when a deal was not struck.
The livewire forward has played all 11 games for the Giants so far this season, kicking nine goals.
Carlton defender Sam Docherty and North Melbourne midfielder Ben Cunnington have also dealt with bouts of testicular cancer over the last year.