Keath hobbled off the ground during the first quarter of the Bulldogs' win over Melbourne on Saturday night, which saw them replace the Demons on top of the ladder.

Versatile tall Josh Schache stepped up in Keath's absence to play an important defensive role in just his second senior appearance of the season.

The Bulldogs are guaranteed a finals berth and can make the September run a little easier on themselves by locking in a top-two spot.

They face Adelaide, Essendon, Hawthorn and Port Adelaide in the last four home-and-away rounds, but will be without Keath for at least three of those.

"Although low grade, I expect Alex to miss the next three to four games of footy," Bulldogs head of sports medicine Chris Bell said.

Former captain Easton Wood looms as Keath's natural replacement against Adelaide this week, having overcome an ankle injury.

The Bulldogs are hopeful Keath, Stefan Martin, Adam Treloar, Lin Jong and Ryan Gardner will all be available for the finals campaign.

Ruckman Martin has played just once since round seven, hurting his shoulder on return from an Achilles injury last month.

He has been sidelined by a groin injury in recent weeks but is now listed as being three or four weeks off a return.

Treloar (ankle) could return within a fortnight, while Jong (hamstring) and Gardner (shoulder) are listed as being two to four weeks away.

The unlucky Ed Richards is also unavailable this week because of concussion suffered in a collision with Melbourne's Kysaiah Pickett.

Richards has played just four matches this season after missing three months with an ankle injury.

"Ed was involved in a contest where he clashed heads," Bell said.

"This caused him to have some concussion symptoms.

"Ed has come in well today and we'll work through a process in the next 10 days or so to determine his availability."

Australian Associated Press