Rory Lobb and Michael Walters both came off the field with apparent injuries during Fremantle's AAMI Community Series clash with West Coast at Optus Stadium.
In the opening term Lobb appeared to have hurt his right knee after going down in a tackle on Fremantle's attacking 50.
The tall forward / ruck was then helped off the ground with the help of the club's medical staff.
The medical staff have confirmed that Lobb has sustained a knee injury and the 28-year-old will be sent for scans to determine the severity.
Walters came off in the third after grabbing at his right hamstring.
At the three quarter time huddle the forward was in the huddle with his teammates with ice on his hamstring.