As anticipated, Robin van Persie and David de Gea both miss Saturday's opener in Bangkok after being given additional time off following their summer international commitments, although they are due to join up in Sydney.
However, Vidic's non-appearance was not expected and there was no immediate explanation from the club.
There was no hint of any problem on Friday when Vidic attended the official unveiling of David Moyes as Sir Alex Ferguson's successor.
And while his absence may be connected to the treatment received by the Serbian on the chronic knee injury that ruled him out for virtually 12 months, any fresh problem would be a concern.
In addition to Van Persie and De Gea, Shinji Kagawa will also be a late arrival, linking up with his team-mates in Japan on July 21 after a rest following his country's Confederations Cup campaign.
- Disease & Medical Conditions
- David Moyes
- David de Gea
- Robin van Persie
- Chris Smalling
- Ashley Young