Brendan Rodgers has held talks with Jozo Simunovic over his Celtic future.
In September the defender was given a new contract but after the 4-0 defeat away to Hearts Kris Ajer has taken his place in the team and become the club’s first pick defender.
Simunovic has only came back into the side following Dedryck Boyata’s injury at Kilmarnock and has shown both sides of his game.
Against Zenit St Petersburg he barely put a foot wrong but was at fault for both of the goals lost against Partick Thistle.
“I’ve had a good chat with Jozo and reiterated to him that he will not achieve the levels I think he can get to if he’s not concentrated,” Rodgers told the Daily Record.
“It’s as simple as that. It doesn’t matter if it’s Partick, St Petersburg or St Johnstone – you have to be concentrated in your game.
“You saw him on Thursday night, he was brilliant but that’s what you have to be here.
“He’s only 23 and Kris is just 19. We’ve got Kieran Tierney at 20, Eboue Kouassi is 20, with Olivier Ntcham and Moussa Dembele 21 but their maturity they showed against Zenit was very pleasing.”
Rodgers is likely to change the back four today with Jack Hendry coming in ahead of a vital week.
On Thursday Celtic face the second leg of the match against Zenit followed quickly by a vital Premiership clash against Aberdeen at Pittodrie.
Boyata is unlikely to be fit for those matches leaving Rodgers to operate around three central defenders through a crucial schedule of matches.