Scans have shown that Morgan has suffered cruciate ligament damage.
Morgan sustained the injury in the 1-0 defeat by Coventry City on Saturday.
Sheffield United boss Gary Speed told the club’s official website: “It’s a massive blow for both Chris and the club and realistically we won’t see him in action again until pre-season training next July.
“The lads we have that can play in the central defender’s role will miss his experience and spirit, but I’m sure they will do all in their power to make up for his absence.”
