Steve Bruce has admitted it is a major blow to lose Sunderland goalkeeper Craig Gordon for three months.
Gordon is set to be sidelined until February after breaking his arm in a challenge with Tottenham striker Jermain Defoe a fortnight ago.
Having struggled to establish himself in the side at the start of the season, Gordon had just begun to produce his best form when the injury struck.
"He was starting to look like the goalkeeper we paid all that money for," said Bruce.
"Of course he's upset, he's got a broken arm. He's had an operation to have a plate inserted and he's in plaster.
"To have him out for three months is a big blow, for sure.
"He is devastated with what happened but he will get over it."
Defoe has apologised and insisted the clash was accidental but Bruce is not sure whether he could have done more to avoid Gordon.
"When I first saw it with the naked eye I thought it was 50-50," said the Black Cats manager.
"However, when I looked at it again - could Jermain Defoe get out of the way? He is the only one that can answer that."
The suspended Michael Turner will be another player missing for Sunderland when they take on Arsenal at the Stadium of Light on Saturday but John Mensah could be available again.
The Ghanaian defender has been struggling with a calf injury but Bruce is optimistic he will be fit to replace Turner.
"John's resumed full training after what has been a really frustrating time for him where he has been there or thereabouts for several weeks in terms of full fitness, only to keep picking up one niggling injury after another," he told the Sunderland Echo.
"But he resumed full training this week and it's just a case now of seeing how he comes through.
"I know he's been out for a while but if he's fit I'll have no qualms about playing him because he's one of those players who are in naturally great condition and who are never far away from being fit enough.
"He's a natural athlete and if he comes through this week alright he'll come into the reckoning."