Kalas missed Saturday’s win at play-off rivals Derby due to a minor hip injury, withDenis Odoi starting in his place.
Otherwise, bossSlavisa Jokanovic is expected to choose from an unchanged squad after reporting no new injury concerns.
The in-form Cottagers, five points adrift of the top two, will bid to extend their unbeaten league run to 14 matches.
Sheffield United boss Chris Wilder is hoping to have almost a full-strength squad at his disposal.
Wilder confirmed two unnamed players will have late fitness tests, but David Brooks, Ricky Holmes and James Wilson would all travel.
Midfielders Brooks and Holmes have been struggling with respective back problems, while Wilson has had an ankle injury.
Goalkeeper Jamal Blackman and top scorer Leon Clarke are hopeful of recovering from minor injuries sustained in the recent win at Reading. Paul Coutts (knee) is the only long-term absentee.