Birmingham goalkeeper Nico Vaesen will be sidelined for nine months with a knee injury.
Vaesen snapped a cruciate ligament in his right knee late on during the derby win against Aston Villa.
He collapsed in agony clutching his knee after making a clearance and underwent an operation which revealed the extent of the damage.
Long-serving Ian Bennett will now take the number one mantle for Birmingham with Australia Under-23 international Clint Davies as his deputy.
Bennett's contract at St Andrews expires at the end of this season and the next nine games of the Premiership season could have a major say on his future at the club.
Manager Steve Bruce attempted to bring in an experienced understudy for Bennett.
But a request to the Premier League for special dispensation to sign a keeper outside the transfer window was rejected.