Greg Taylor’s move to Celtic from Kilmarnock is in doubt, Sky Sports News understands.
The left-back is currently awaiting news while with the Scotland squad in Edinburgh preparing for the European Qualifiers double-header against Russia and Belgium.
It is understood that the Kilmarnock defender underwent a medical ahead of the proposed move to Celtic on Saturday.
Neil Lennon said after Celtic's 2-0 win over Rangers that he was "hopeful" Taylor would sign before Monday night's deadline, but that there was "a hold up at the Kilmarnock end".
Kilmarnock and Celtic also remain in talks over the possible season-long loan of Jack Hendry and the permanent deal of Calvin Miller.
Kilmarnock have also confirmed that Kirk Broadfoot has left the club after 78 appearances for the Ayrshire side.
Broadfoot signed a three-year contract in 2017 after leaving Rotherham but is now a free agent. The former Rangers and Scotland defender made six appearances for Kilmarnock this season.
Elsewhere, it is understood that Celtic are interested in signing Jeremie Frimpong from Manchester City on a permanent deal.
The 18-year-old can play at right-back and left-back. He has yet to feature for the Manchester City first team.