Brendan Rodgers has one very important decision to make in defence for the return leg with Valencia.
It doesn’t involve the full-back positions – Jeremy Toljan and Jonny Hayes seem certain to start – but in central defence the Celtic boss has to decide who plays alongside Dedryck Boyata.
In the first leg Jozo Simunovic was pulled all over the place with Valencia’s second goal delivered by an unmarked Ruben Sobrino shooting home from seven yards out. At that moment the odds on Celtic progressing became ridiculous.
On Sunday at Kilmarnock Kris Ajer replaced Simunovic, who has made just one appearance on a plastic pitch since joining Celtic in 2015.
The former Dinamo Zagreb defender has never quite convinced the Celtic support that he is the real deal. Apart from one memorable challenge on Kenny Miller there have been few domineering performances in between regular spells out injured. According to Transfermarkt he has had eight absences due to injury.
By contrast Ajer has always made himself available – away to Astana in the 2017 Champions League qualifier he learned some punishing lessons as Celtic leaked goals but just managed to hang on to claim a place in the group phase.
Ajer is effectively in his second season at Celtic, deputising behind Boyata and Filip Benkovic who are the first choice pairing but about to leave the Hoops in the summer.
The young Norwegian has had some testing times but 90 minutes against Valencia will have him fully prepared for next season’s Champions League qualifiers – assuming Celtic clinch the title.
None of next season’s Champions League opponents will be on a par with the Spanish side. This season Celtic would have faced qualifiers against the champions of Greece and Hungary to reach the group phase.
Rodgers has spoken recently about age not being a barrier – giving Ajer the jersey to face Valencia is a sound decision for the clash in the Mestalla with plenty of dividends down the line for the player and club.