Smiles can’t conceal the frailties that dog Celtic

However, without Boyata, the options of Ajer, Simunovic, Nir Bitton and Jack Hendry – new and wholly untried in Europe – hardly inspire much confidence.

Simunovic, in particular, seems to be entirely lacking in the conviction and physical strength he had a year ago.

After Forrest had seemed to settle the tie with two goals in nine minutes, he allowed Thistle back in to the contest courtesy of a passback that proved a gift for Kris Doolan.

In the closing minutes, with Forrest having completed his triple, he was then embarrassingly out-muscled by Conor Sammon.

It may be that Rodgers con- siders switching to a back three on Thursday, even if Ajer, pictured, wants to give the impression that he won’t buckle under the pressure Zenit will exert.

In fairness, he seems a much more competent defender than the freshman who, in tandem with his partner, Bitton, crumbled as Celtic conceded four goals in their Champions League qualifier in Astana last August.

“For me, being 19 years old, every single game is big,” Ajer said. “It won’t make a change who we play against. I’ll always try to do my best. I think the gaffer has a squad here that really knows their job. Everyone is ready when they’re called upon. If I get the chance on Thursday I will be ready.”

Ajer’s clip watching reflects his diligent quest for constant improvement. “I do that for every game. That’s how I work. I look at the details, I look at the goals. I look at when I’m with the ball to find easier solutions next time. “That doesn’t change from game to game. With the Thistle game it would be me sitting until the evening but when you play I think that’s a big part of the game.

“You must watch it and learn from your mistakes, and what you did well too. I go back and forth to learn things then I have a chat with the staff on the Monday when we meet again. It’s good and it helps me a lot.”

The tragic passing of former player Liam Miller at the tender age of 36 cast a shadow over Saturday’s proceedings. A minute’s silence was observed, the Celtic players wore black armbands to mark their respect and Rodgers and Forrest both offered heartfelt sympathies.

The Celtic winger was rightly described as the game’s “class” performer by his manager. He exhibited that class in the respect he gave to Miller.

The Cork-born midfielder will be remembered best in Celtic colours for his outstanding European displays against Lyon and Anderlecht.

Forrest will make his 67th European appearance for Celtic against Zenit. He is the man most capable of making the iconic number mean something this week.