But Sebastian Larsson - the player Bentley could replace if he leaves - may soon be heading out of St Andrew's with Newcastle given permission to speak to the Sweden international.
Manager Alex McLeish has not given up hope of signing Rangers striker Kenny Miller, who is also a target for Fiorentina.
The Blues boss confirmed: "Bentley is doing a medical. It might run into two days. It will be good to sign him because he has got a bit of quality and class as a footballer. His delivery at set-pieces is excellent as well. He is a natural footballer."
Larsson is out of contract in the summer and a new offer from Blues has remained unsigned.
McLeish said: "The latest with Seb is we gave his advisor permission to speak to Newcastle. Other than that, I've heard nothing.
"We came to a kind of impasse (over a new contract). I know Seb would like to stay but we'll just have to wait and see. There is nothing I can really add to that."