Morison was replaced at half-time during the midweek draw with Peterborough due to a calf strain and defender Lees was forced off in the first half with a hip problem.
Jason Pearce will continue alongside skipper Lee Peltier in central defence if Lees is ruled out.
Striker Ross McCormack is also rated doubtful after taking a blow to his head on Tuesday night, while manager Neil Warnock revealed goalkeeper Paddy Kenny, midfield pair David Norris and Michael Tonge, plus defender Sam Byram are all nursing knocks.
Striker El-Hadji Diouf impressed as a second-half substitute in midweek and is pushing for a recall to the starting line-up and midfielders Michael Brown and Rudy Austin also provide Warnock with alternative options.
Leeds are bidding to kick-start their play-off challenge with victory after three straight draws.