Celtic are considering a move for Arsenal left-back Kieran Tierney next month.
Sky Sports News understands the Hoops are exploring a pre-contract and loan offer for the Scotland international.
Arsenal are expected to listen to offers for Tierney in the January transfer window, with the club not expected to trigger the one-year contract extension in his current deal.
There is currently no agreement on a new contract for current Celtic left-back Greg Taylor, with his deal due to expire in the summer.
Celtic also have Barcelona left-back Alex Valle on a season-long loan deal.
A number of clubs across Europe are also said to be interested in Tierney, who Arsenal from Celtic in 2019 in a deal worth around £25m.
Why a Celtic return might tempt Tierney
Tierney made more than 170 appearances for Celtic and won five Scottish Premiership titles during his time with the club.
Speaking to The Currie Club podcast with Darrell Currie in 2022, Tierney did not rule out a return to Celtic.
"I think when a player who loves the club leaves, there's always that, 'what if he comes back', and you can't rule anything out," he said.
"I'm always going to love Celtic, I'm always going to support Celtic, so you never know in football.
When does the winter transfer window open and close?
The 2024 winter transfer window for both English and Scottish league clubs officially opens on Wednesday January 1.
Transfer Deadline Day actually falls on Monday February 3 2025. The English window closes at 11pm UK time.
Transfer Deadline Day for most major European leagues - including France, Germany, Italy, Spain and Scotland - is also Monday February 3 2025.
