Arsenal midfielder Lansbury has missed the last two games with a hip injury and Manchester United centre-half Cathcart sat out last weekend's defeat by Derby with a knee problem.
Jon Harley will keep his place in the starting line-up if Lansbury is ruled out while club captain Jay DeMerit should start again at the back.
The USA defender started his first game since August against the Rams having recovered from eye surgery.
Teenage midfielder Ross Jenkins is still sidelined after undergoing a back operation.
Mackay and his side are playing under the cloud of possibly going into administration, which will see them deducted 10 points and plunged towards the relegation zone.