Aberdeen are understood to have rejected a bid from Celtic for Scott McKenna, believed to be in the region of £3.5 million.
The Dons have vowed not to sell the Scotland international in this transfer window, and have already rebuffed approaches from Hull City.
The 21-year-old, who is currently out injured with a hamstring problem, has been a target for Celtic in recent months.
The Hoops are working on defensive reinforcements, with Dedryck Boyata’s future still unclear amid interest from Sevilla and Fenerbahce.
Aberdeen threw out three offers from Hull during the last transfer window in January, with the player signing a new deal in March, keeping him at Pittodrie until 2023.
Swansea City were also thought to be interested earlier this summer.