The 21-year-old, who is on loan from Middlesbrough, limped out of last weekend's trip to Barnet with a knee injury and is a doubt.
Should Walker be unavailable, he may be joined on the sidelines by striker Drewe Broughton who missed out against the Bees due to a chest infection.
Stephen Brogan could be among the substitutes, though, after returning from an ankle injury in the reserves' final game of the season while Andy Liddell, who has not played for the first team since October, may also be in contention.
Striker Tom Pope and defender Dale Tonge are nursing foot injuries that will keep them out for the rest of the season.
Victory for Rotherham would secure a place in the play-offs.