Goalkeeper Hamer has made 65 league starts for the Bees in three separate loan spells from Reading and returned this week for a fourth stint at the club.
However, former Watford keeper Richard Lee is expected to keep hold of the gloves for the time being so Hamer will be on the bench against the Owls.
Winger Sam Wood could be involved after recovering from a back injury, while summer signing Kirk Hudson is also close to full fitness following the groin injury which has delayed his debut.
Striker Carl Cort has recovered from an Achilles injury and should be involved again while strikers Charlie MacDonald and Gary Alexander will hope to be recalled after being rested for the Johnstone's Paint Trophy win at Stevenage in midweek.
The match kicks off at 12pm.