The former Arsenal player has been dogged by injury problems and suffered his latest setback during the closing stages of last weekend's 2-0 home reversal against Fulham.
It has emerged Hleb suffered ligament damage and he is ruled out of the final game of the season against Tottenham at White Hart Lane on Sunday.
Hleb had already made it clear last month he had no desire to extend his season-long loan with Blues.
The midfielder had previously sustained hamstring and knee setbacks and he was only able to show flashes of the form evident during his spell with the Gunners.
Blues boss Alex McLeish is sweating over the fitness of several players ahead of the Spurs clash.
Lee Bowyer (hamstring), Stuart Parnaby (groin) and Martin Jiranek (ankle) are all doubtful after being substituted against Fulham while Cameron Jerome (heel) is also injured.
In addition on-loan Tottenham winger David Bentley is ineligible to face his parent club.
Source: PA
Source: PA