Aston Villa manager Paul Lambert confirmed his interest in the Middlesbrough defender on Tuesday and said he was hopeful of completing a deal.
Boro boss Mowbray does not want to lose a player he rates so highly but accepts that everybody has their price.
"We've had a few conversations with Aston Villa over the last few days, but he's not a player we're in a hurry to move on," he told the club's official website.
"He's done exceptionally well for us and is a very talented individual. But like all players, if the numbers get to the right level, we will consider it."
Marvin Emnes is another player to have been linked with a move away from Middlesbrough, with Swansea City understood to be keen on bringing in the striker.
However, Emnes was included in the Boro side for Tuesday's Capital One Cup clash against Gillingham and Mowbray had no hesitation in picking him.
The manager said: "I've seen the speculation and I've heard the rumours and yet Marvin's fit, he trained on Sunday and Monday, and there was no reason not to play him and here he is playing."