McLeish brought the well-travelled forward to St Andrew's from Charlton in a £1million move in 2008.
But the 32-year-old has fallen down the pecking order and spent the first half of the campaign on loan at local rivals Wolves.
Bent's current agreement with the Molineux club ends next month but McLeish has made it clear his days at Blues are numbered.
The Blues boss told Press Association Sport: "Marcus knows he does not have a future here at Birmingham.
"He will be trying to get a new club in January."