Albion boss Oscar Garcia fears a long lay-off for Andrew Crofts and may now have to consider signing a midfield replacement.
Crofts left The Amex on crutches tonight after suffering a serious-looking knee injury in the second half against Birmingham.
The Welsh international had to be carried off and his plight marred for Oscar a 1-0 victory which lifted the Seagulls to sixth, the first time they have been in the play-off zone this season.
Crofts twisted awkwardly as he attempted to tackle Birmingham sub Reece Brown. He punched the ground in anguish before being helped off.
Oscar said: "I'm not sure 100% but it's a bad injury for sure.
"He'll have to have a scan and we'll have to wait for the results. That was the worst news today. We won but the other side is Crofty being injured."
Oscar, asked if signing a striker in January is the priority after Ashley Barnes joined Burnley, said: "Yes, and a midfielder for Crofty. We'll have to see what we need and we have to decide if it is possible to sign some new faces or not."
Liam Bridcutt, wanted by Sunderland and the subject of a rejected transfer request, was not in the squad due to an injury which also ruled him out of last Saturday's FA Cup tie against Reading.
Oscar confirmed: "He is carrying a groin injury and he wasn't 100%. We needed people who are 100%. He is a Brighton player and he will be avaiable for selection when he is 100%."
Oscar also confirmed David Lopez was at risk of being replaced by Solly March just before volleying in Albion's second half winner.
The head coach said of his fellow Spaniard: "We had two options and one was him."