The Serbian centre-half is currently on the sidelines after undergoing an operation, and the Red Devils were beaten 3-2 at home by Tottenham on Saturday.
The Old Trafford skipper missed the majority of last season with a cruciate ligament injury, and as such Sir Alex Ferguson’s men relinquished their title to Manchester City.
Shearer feels Vidic’s absence will be critical in determining who will be English champions for 2012-13.
“It is early days in the title race but already Manchester United have been dealt a huge blow from which they will not recover,” Shearer stated in his column in The Sun.
“Before the season started I did not think they were strong enough to win the title despite all their new signings.
“With the loss of Nemanja Vidic now for two months I am even more convinced that the Premier League trophy will either be staying put or heading to Stamford Bridge.
“In truth his loss last season probably cost them the title. For me they are looking a lot more vulnerable now,” he concluded.
By Gareth McKnight