Sunderland manager Steve Bruce says goalkeeper Simon Mignolet has fractured an eye socket and faces a longer spell on the sidelines than first expected.
The Belgium international underwent surgery on a broken nose after Saturday's 2-2 draw with Aston Villa, where further damage was discovered.
"Rather than a couple of weeks, it will be a couple of months," said Bruce.
With Mignolet out, Bruce has recalled Trevor Carson from his loan spell at Bury as cover for Keiren Westwood.
"The broken nose is as bad as I've ever seen, and he's fractured the eye socket as well," Bruce told BBC Newcastle.
Mignolet, 23, was withdrawn after a second-half collision with forward Emile Heskey and replaced by summer signing Westwood, who made a key save to deny former Black Cats striker Darren Bent.
The 27-year-old Republic of Ireland international is now Bruce's first choice with Craig Gordon also sidelined, and is also in line for his first Premier League start at Manchester United on Saturday.
"That's the reason why I brought in a goalkeeper of Keiren Westwood's ability," Bruce continued.
"He's waited patiently for his chance, he's done extremely well on Saturday and he's waited a long time to play in the Premier League.
"Here's his big opportunity and I think he'll grasp it."
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