Steven Reid is to miss six weeks of the season after tearing a cartliage in Saturday’s defeat to Manchester United.
The former Republic of Ireland international was substituted just after the hour mark and will now undergo surgery to repair the tear later in the week.
Reid omission provides Roberto Di Matteo with another selection headache ahead of tonight trip to Fulham with Gabriel Tamas suspended and Jonas Olsson and Pablo Ibanez both injured.
"He is an important member of our squad and was playing well until he was forced off,” said the Albion head coach.
"The big thing about Reidy is that he offers cover for so many positions.
"He's likely to be out for a minimum of six weeks and all we can do is wish him well with his surgery and a speedy recovery.
"Pablo's hamstring was playing up on Saturday and he couldn't continue but it looks as though we caught the problem early as the scan results are very positive.
"We'll just have to assess him on a day-to-day basis.
"We're going to be even thinner on the ground than we already were in defence tonight but we're just going to have to pull together and give it our best shot."