The Scot is facing a lengthy spell on the sidelines after damaging knee ligaments while on loan with the Clarets, and he is now back at the Stadium of Light where the Black Cats physios are overseeing his recovery.
The player's future is now on hold until he returns to full fitness but Coyle says he would definitely be interested in signing him again if he makes a full recovery.
"If and when he's back fit, I would love to have Russell here on a permanent basis," he told the Sunderland Echo. "I have a real belief in him. I think he's a top player and he's a fantastic man."