The left-back was caught up in a collision during the closing stages of Saturday's crucial 1-0 win at Watford and will now watch on from the sidelines as Blues go in search of automatic promotion over the last two games.
Franck Queudrue is expected to shift into his more favoured position on the left-hand side of defence for Saturday's promotion showdown against Preston, with Djimi Traore likely to get the nod over Martin Taylor at centre half.
Speaking about Murphy's injury, Alex McLeish told Birmingham's official website: "He's going to get it pinned and we believe he could be back for the start of pre-season.
"We are disappointed for David, obviously we have lost a player who was coming back to full fitness and had done very well in the last couple of weeks.
"But we have coped admirably with the absences in the past and now there is a chance for Djimi Traore to show all his massive experience in high-level football."