Scans confirmed this week that McKay would require an operation on his knee after experiencing soreness, with the 2021 Coleman Medal winner set to go under the knife on Thursday.
Carlton Head of Football Brad Lloyd expressed his disappointment in the star spearhead's setback.
“This news is obviously unfortunate for Harry, given the really strong start to the season he was having both personally and as a leader for our side,” Lloyd told Carlton Media.
“Harry will have the surgery tomorrow morning, he’s the ultimate professional so will attack his rehab to be in a position to make an impact when he returns to the side, which at this stage we expect to be around three weeks after the bye.”
McKay and partner-in-crime Charlie Curnow have paired to boot 45 goals to start this season, with more of the workload set to shift to the latter's shoulders for the coming rounds.
The Blues have also confirmed that young defender Luke Parks will be sidelined for 12 weeks after suffering a bone stress injury in his foot.
“We had hoped for a better outcome with Luke but unfortunately we will be without him for an extended period of time,” Lloyd added.
“He is a great character, so we know he’ll put everything he can into getting himself fit and available late in the season.”
The pair of setbacks add to an extensive injury list at Ikon Park, with Jack Martin (calf), Liam Stocker (shoulder), George Hewett (calf), Mitch McGovern (hamstring) and Marc Pittonet (knee) among those currently residing in the casualty ward.