Turnbull, Scotland’s Young Player of the Year, is expected to complete his move to Celtic within the next 24 hours after Motherwell agreed a club record fee for the 19-year-old midfielder on Wednesday.
Celtic manager Neil Lennon fully expects Turnbull, who scored 15 goals in a stellar season for Motherwell, to be capable of immediately holding down a regular starting place for the eight-in-a-row title winners.
The recruitment of Turnbull may make Celtic more willing to consider any bids from English Premier League clubs for McGregor this summer.
The Scotsman understands there is firm interest in the Scotland midfielder, who celebrates his 26th birthday on Friday, from his former Celtic manager Rodgers as he prepares for his first full season in charge of Leicester City. Rodgers is expected to sanction an offer in the coming weeks for McGregor who is valued at around £10 million by Celtic.
Brighton and Watford are also monitoring McGregor’s situation. He signed a new contract with Celtic as recently as last December, which runs until 2023, but it is believed he has ambitions to play in the English Premier League at some stage of his career.
Leicester would appear to stand the best chance of persuading McGregor to make the move now as he would welcome the prospect of furthering his development once more under Rodgers’ tutelage.
McGregor has been a key figure for the Celtic side which has won three consecutive domestic trebles and his departure would not be popular among supporters.
But, as Lennon reshapes the squad following his appointment as permanent manager for a second spell, he has inherited a squad with a surfeit of central midfield players.
Celtic captain Scott Brown will continue to be a first pick in that department under Lennon, while Ryan Christie and Tom Rogic are also likely to be integral to his plans. Lennon remains an admirer of Nir Bitton, whom he signed during his first spell as manager, and has high hopes for 19-year-old Ewan Henderson.
The future of Olivier Ntcham, linked with a move to Marseille, is less certain while Youssouf Mulumbu and Eboue Kouassi have both struggled to make an impact and may also be regarded as surplus to requirements.
While McGregor would certainly not feature on any list of players Lennon would too readily wish to move on, the arrival of Turnbull does make it more palatable for Celtic to contemplate accepting an offer from Leicester which meets their valuation.
Celtic’s search for a new central defender, meanwhile, has turned to Christopher Jullien of Toulouse. The 26-year-old, valued at around £8 million by the French club, is also a target for Spanish outfit Celta Vigo.