The Scottish striker has been in fine form this season and his goals have spearheaded Wednesday into a play-off position.
But the star forward fractured a bone in his foot against Doncaster Rovers at Hillsborough and limped off.
MacLean did have hopes to be back for the Hull game on Saturday but after seeing a specialist, it was judged that he does not need an operation, just long recuperation.
He initially told Footymad that he hoped to be back for the play-offs but that now is not the case.
Hopefully he makes a speedy come back and is in line to carry on his exploits next season.