Alex McLeish says that he needs Nigel Quashie to prove his fitness before he commits to taking him on loan.
The West Ham midfielder has been training with the Blues squad for the past two weeks.
McLeish had hoped to play Quashie in Blues' Reserve game against Manchester United on Tuesday night but the player was forced to pull out of the fixture because of a tight hamstring.
The former Scotland international missed the whole of the 2007/08 season with a persistent foot injury, so McLeish is understandably keen to see that the 29-year-old can play on a regular basis.
"He's (Quashie) training with us, but he's been out of football a long time," said Alex McLeish.
"He would have played in the game against Man Utd because we'd got permission from West Ham, but in his search for fitness he's picking up little niggles and his hamstring was tight so he didn't play.
"But we'll see how he develops in the next week or two.
"I know what sort of player Nigel is, he's a decent player and I'm sure if he proved his fitness he could be a good addition to the squad but we need to see just how fit he is and we'll be doing some tests on him in the next week or so."
The Blues boss also confirmed that he had yet to make a decision on Dutch triallist Arturo Ten Heuvel.
The 29-year-old midfielder played for the Reserves on Tuesday night against United.
"He did alright," added McLeish.
"I thought he was very tidy and he passed the ball well.
"He's out of contract and if we made the move it wouldn't be a problem in terms of bringing him in, but I've not spoken to him yet because I've not made a decision yet."