Purkiss, having struggled with a hamstring injury of late, travelled with the Saddlers for Saturday's goalless draw at Brentford but failed a late fitness test.
With James Chambers also missing out at Griffin Park due to an ankle problem, the right-back berth was handed to debutant George, who duly impressed.
Chambers will again sit out against the Cumbrians and should Purkiss not make it then George will be called on for his second start in four days.
The versatile Richard Taundry is expected to return to training next week following his ankle complaint.
Walsall have only lost two of their last 13 games but have now drifted nine points off the play-off places.