Vidic was hurt in Sunday’s 2-1 win at West Bromwich Albion, but Ferguson initially expected him to be out for just two weeks.

Vidic will miss Serbia’s European Championship qualifiers at Northern Ireland on Sept. 2 and against the Faeroe Islands four days later.

There was better injury news for United, with Rio Ferdinand now potentially returning from a hamstring injury for the 28 August match against Arsenal.