Thatcher will be out for a month

The 28-year-old missed Monday night's 1-1 draw with Norwich after suffering a reaction to an ankle injury in training last weekend.

He went for a scan this week which showed he needed an operation to remove some floating debris in the problem area.

Thatcher misses Sunday's Manchester derby and is sidelined for four weeks.

The news is is the latest injury blow for Keegan, who has learned he will be without Trevor Sinclair for the remainder of the campaign.

With Sun Jihai also out for the season after rupturing his cruciate ligaments against Chelsea last month, it means 22-year-old Warrington-born defender Stephen Jordan is set for an extended run in the side after he made his first Premiership start against the Canaries.