Northern Ireland international Duff suffered a calf strain in the warm-up before his side's 3-2 victory at Sheffield United on Saturday and is rated doubtful while midfielder McCann is suffering from illness.
However, defender Clarke Carlisle returns from suspension and will take his place in the centre of defence alongside Steven Caldwell at Turf Moor.
Young striker Alex McDonald came off the bench to impress against Kevin Blackwell's side in what was his first league appearance of the season, but he will have to settle for a place on the bench once again with Robbie Blake and Martin Paterson continuing in attack.
The Clarets go into the match on the back of a three-game unbeaten run in all competitions with victories against Derby, Arsenal and the Blades, which has helped catapult Coyle's men into fourth spot in the Championship.
Cardiff will be without leading scorer Ross McCormack for the crunch clash.
McCormack is awaiting the results of a scan on a hamstring injury but he is not expected to play any part at Turf Moor, although boss Dave Jones has stressed it is not the same injury that recently sidelined him for three weeks.
Fellow striker Jay Bothroyd (hamstring) and defenders Roger Johnson (groin) and Mark Kennedy (hamstring) also picked up knocks during Saturday's 2-0 win over Preston and are battling to be fit.
On-loan striker Michael Chopra stepped off the bench against North End despite having missed training last week with illness, and he is okay to feature from the off this time around.
Midfielder Stephen McPhail will serve the final game of his two-match ban, leaving Joe Ledley to continue wearing the captain's armband, while Peter Enckelman will look to keep his place in goal.
Striker Eddie Johnson has returned to training and could feature, left-back Tony Capaldi (knee) continues to build up his match-fitness but is not yet ready, while midfielder Peter Whittingham remains sidelined.
Sporting Life