Southampton goalkeeper Antti Niemi has undergone keyhole surgery, dealing a major blow to Saints' relegation fight.
The Finn suffered a minor cartilage tear in training and will miss three weeks at a vital stage of the season.
Niemi will sit out the derby with Portsmouth and the clash with fellow strugglers Norwich, possibly returning against Crystal Palace.
Physio Jim Joyce told Saints website: "He's got an outside chance of facing Palace, it depends how he recovers."
So urgent was Southampton's rush to get Niemi operated on he was prevented from having lunch at their training ground so he could go under anaesthetic on Monday night.
Niemi, rated among the Premiership's top keepers, opened up his knee joint blocking a shot in training last Thursday.
He missed the 2-2 draw with West Brom and Saints were prepared to rest him from the Carling Cup tie at Watford.
Deputy Paul Smith is still recovering from a broken thumb, and third choice Alan Blayney will continue to deputise.
Southampton will be wrapping him in cotton wool as youth team keeper Michael Poke - who will be on the bench at Watford - is recovering from a broken finger.
Physio Joyce added: "Antti had keyhole surgery on Monday night which was the earliest we could get it done.
"From our previous experience of similar operations, we would expect him back in training in three weeks."