The Norwegian international had scored his first domestic goal of the campaign before Gabriel Agbonlahor sealed victory with his third strike in four games against Everton.
O´Neill said: "We don´t know the extent of the damage at the moment but it doesn´t look great. He has damaged his ligaments but he will get scanned on Monday."
Copyright (c) PA Sport 2007, All Rights Reserved.
Do YOU want to write for GiveMeSport? Get started today by signing-up and submitting an article HERE: https://www.givemesport.com/writeforgms