Kozluk, sidelined since late January with a knee injury, has returned to full training with the Tykes this week and could be included.
Hammill missed the midweek defeat at Bristol City due to a hamstring strain, but is expected to be back in contention.
Manager Mark Robins is still without on-loan Stoke defender Carl Dickinson, who has returned to his parent club for treatment on damaged knee ligaments.
In Dickinson's absence Stephen Foster is likely to continue alongside Ryan Shotton in central defence, with Luke Potter and Bobby Hassell making up the back four.
Barnsley's outside play-off hopes have nose-dived in recent weeks, with Robins' side losing three of their last five league matches.