Aston Villa midfielder Chris Herd has broken down on-loan at Wigan Athletic.
Herd has been ruled out for the season with medial ligament damage.
"Chris looks as though he has an issue with his medial ligament which could see him maybe needing surgery and missing the rest of the season," said Mackay.
"It's another situation we're just going to have to deal with, but they seem to be coming thick and fast at the moment.
"He's been fantastic since he's been here, he has a huge character and his performances have been excellent."
