O'Grady has scored twice in eight appearances for Barnsley since arriving in January, but will not feature at Hillsborough.
Manager David Flitcroft is expected to choose two from Chris Dagnall, Jason Scotland and Marlon Harewood to start up front in O'Grady's absence.
Midfielder Stephen Dawson, on the bench in the two previous matches, is hoping to make his first start since damaging ankle ligaments in January.
But the Reds will be without injured defenders Jim McNulty and Scott Golbourne.
McNulty has missed the last five games with an ankle injury, while Golbourne's season came to an early end last month due to knee ligament damage.
Defender Bobby Hassell is pushing for a recall after heading the winner against Watford last time out, while midfielders Tomasz Cywka and Ryan Tunnicliffe, on loan from Manchester United, are also in contention.