Fremantle midfielder Connor Blakely is expected to miss about six weeks of AFL action after injuring his right knee at training.
Blakely will undergo an arthroscope to determine the extent of the damage.
"The medical advice at this stage is that Connor has damaged the meniscus in his right knee and we are awaiting the results of an arthroscope," football operations manager Chris Bond said on Wednesday.
Blakely has played every match so far this season, averaging 23.8 disposals a game.
He was particularly influential in recent wins over Adelaide and Carlton, tallying a combined 14 clearances and 57 disposals in those games.
Fremantle aim to make it three straight wins when they host Brisbane at Optus Stadium on Sunday.