WESTERN Bulldogs key defender Alex Keath will be sidelined for at least the next six weeks after straining his hamstring in Friday night's loss to Brisbane, but Ed Richards has now cleared concussion protocols and is set to return against Fremantle on Saturday.

Keath came off the ground in the closing minutes of the loss to the Lions and underwent scans over the weekend, which have revealed more damage than first feared.

The 32-year-old will be sidelined until the end of July at the earliest with a moderate-grade hamstring strain.

After an interrupted summer at the Whitten Oval due to a knee injury, Keath spent the first couple of months of the season playing for Footscray in the VFL before an opportunity opened up in round nine.

Richards missed a second game with concussion after not clearing protocols in time early last week, but the gun defender-turned-midfielder returned to full training on Saturday and has been given the green light to face the Dockers at Marvel Stadium on Saturday afternoon.

With Keath joining Ryan Gardner on the sidelines for a large chunk of the second half of the season, an opportunity presents for former first-round pick Jedd Busslinger to make his debut.

The 2022 No.13 pick spent most of last year developing his body and game after recovering from major shoulder surgery in his draft year, but has taken significant steps forward in recent months, averaging 23.8 disposals and 9.8 marks per game across the past four games for Footscray.

Luke Beveridge might stick with Buku Khamis and play James O'Donnell in defence to start with, but Busslinger will come under consideration during Keath's absence, especially if he continues to improve his one-on-one craft.

Small forward Cody Weightman is on track to return just after the bye in round 15, while key forward Aaron Naughton and recruits James Harmes and Nick Coffield will be pushing to be available within the next fortnight.