Ange Postecoglou has shut down any thought of taking a "trial and error" approach as the Celtic boss looks to find a solution left by the long-term injury to Callum McGregor.
The Hoops host RB Leipzig at Parkhead on Tuesday night knowing a win could fire them back in with a chance of progressing to the last 16 of the Champions League or at the very least gaining third spot which would guarantee Europa League football beyond Christmas.
However, the absence of McGregor in the midfield engine room is a major blow for the Scottish champions and their hopes of progressing in Europe.
Matt O'Riley stepped back into a deep-lying midfield role in the win over St Johnstone, while the likes of James McCarthy and Oliver Abildgaard will also hope for their chance to fill the void left by the crocked Celtic skipper.