Dundee United captain Danny Griffin has undergone minor surgery on a back injury.

It is not known when the Northern Ireland international will be able to return to action.

Griffin had been struggling with the injury since the 3-0 defeat by Rangers in September and has already been sidelined for three weeks.

He will be missing for Saturday's trip to Kilmarnock and his absence will not help caretaker Paul Hegarty's bid to win the manager's post permanently.

United manager Paul Hegarty said: "I can confirm that Danny has had a minor operation on his back.

"He is OK but has been advised to rest by the doctor.

"At this moment in time, we do not know when he will be fit to return, but losing him for any period of time will be a blow."