Michael Frederick has sustained an ankle injury during Fremantle's clash with Brisbane at the Gabba on Sunday.

Frederick pulled up hurt after a marking contest in the first term and was subbed off at quarter time for Connor Blakely.

Senior coach Justin Longmuir said the early signs weren't good for the forward.

"It looks like a syndesmosis. We’ll get it scanned and we’ll get a result out," Longmuir said.

"It doesn’t look great."

Defender Reece Conca also came off in the opening term with an apparent hamstring injury but returned to the field in the second quarter.

Longmuir said it looked like Conca had escaped a serious injury.

"He's got a tight hammy, we'll have to nurse him through," Longmuir on Fox Footy at half time.