Arsenal have been boosted over their pursuit of Celtic fullback Kieran Tierney.

The Gunners have already had a £15m bid rejected for the 22-year-old but are expected to return with an improved offer in the next few days, with Celtic wanting at least £25m for the player.

With Serie A side Napoli also said to be interested in Tierney, it appears almost certain that his future lies away from Celtic Park.

Speaking to BBC Sport, Allan Preston, who is part of the Stellar Group that represents Tierney, said: "It is all down to Celtic – if they get a price that they believe is the correct value for Kieran Tierney he could possibly be on his way.

"No one has hit that price yet."

Preston went on to praise Tierney's character, adding: "I know Kieran really well, I had some food with him the other day.

"He is such an unassuming young man. He is wealthy at the moment but he doesn't possess a watch because he isn't into material things like this.

"He still hangs about with his pals from when he was a youngster, he sponsors his local pub team where his pals play and he's not into his designer gear or anything like that."

Preston continued, "Will there be a time for Kieran Tierney to go? I think that there will be.

"If it's just now it will be up to the clubs that are involved – Arsenal, Napoli or whoever – to then put the money on the table and make Celtic think about this.

"If there is a time for Kieran to go it will be up to Celtic, Peter Lawwell and the board."