It is a cruel blow to the 23-year-old, who broke his leg in 2016 and suffered complications in his recovery that saw him have to wait 672 days between his 21^st and 22^nd senior game.

Pearce, who played State League football for Devonport, had been the rock in defence for Ross Lyon's side this year, with his strong form putting him in the conversation for a spot in the All Australian team later this year.

He had played all 11 games this year, averaging 10.8 touches, 3.3 marks and 2.1 tackles a game.

Pearce hurt his left ankle in what was an innocuous looking incident after a clearing kick from defence.

Second year Docker Stefan Giro will also miss the rest of 2019 after rupturing his ACL over the weekend in the WAFL.

"Stefan has been playing for Peel, working really hard on his craft to try and force his way back into the senior side and Alex has been in outstanding form, and virtually trouble free since returning from that long lay-off after twice breaking his leg," Fremantle general manager of football Peter Bell said on Monday.

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"While it is frustrating for Alex, we know how incredibly resilient and diligent he has proven to be in the past when it comes to recovering from a long-term injury.

"We are confident that Alex will tackle this latest setback with the same level of determination and drive, so he can be back playing as soon as possible."

Pearce, who is a member of the club's leadership group, has played 53 games for the Dockers after being drafted with the 37^th pick in the 2013 national draft.