West Brom skipper Jonathan Greening will be out of action for up to six weeks after a scan revealed he has suffered a strained medial ligament in his left knee.
Greening sustained the setback during the first half of Saturday's FA Cup fourth-round encounter with Burnley at The Hawthorns.
It is the first major injury of Greening's lengthy career and he could be sidelined until the middle of March.
The absence of the former Manchester United and Middlesbrough player will be a major blow to the Baggies' hopes of Barclays Premier League survival.
Albion now have 10 first-team players on the injury list and manager Tony Mowbray described Greening as the most influential player in his two years in charge.
An Albion spokesman said: "Scan results confirm that Jonathan Greening strained the medial ligament in his left knee against Burnley.
"Greening is expected to be sidelined for between four and six weeks."
Mowbray said: "Jonathan has been our most influential footballer in my time here. Him being out for any amount of time is a big blow to us.
"It is his first injury of any note during his career."
However, Mowbray has said he will not bring in additional players on loan to the ones he is already targeting to fill the gaps left by Greening and the other posse of injured players.
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