Stan Lazaridis was stretchered off early in the first half of the game at St Andrews and it has emerged that he will not play again this season after suffering a bad groin injury whilst his replacement Martin Grainger failed to appear for the second half after suffering a recurrence of the knee injury that has plagued him for the last two seasons.
Robbie Savage also finished the game with an ankle injury and looks doubtful for Blues trip to play Portsmouth on Easter Monday.
"Stan Lazaridis and Martin Grainger will not be fit to play again this season," Blues boss Steve Bruce said after the 2-1 defeat to Utd.
"Lazaridis has a groin injury and Grainger has damaged his knee again.