Kristoffer Ajer insists Celtic will be "100 per cent" ready for Aberdeen on Sunday following their Europa League exit in Russia.

The Hoops had travelled to St Petersburg with optimism following last week's 1-0 first-leg win at Parkhead, where Roberto Mancini's Zenit side had looked rusty playing their first competitive game in two months due to their winter break.

However, they soon had the tie back in their own hands on home soil on Thursday night when former Chelsea defender Branislav Ivanovic, celebrating his 34th birthday, put Zenit in front in the eighth minute with a header from a corner.

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Daler Kuzyaev fired in a long-range drive in the 27th minute and striker Aleksandr Kokorin sealed a 3-1 aggregate triumph just after the hour mark.

With European football over for another season, Brendan Rodgers' Ladbrokes Premiership leaders return to domestic chores with a trip to Pittodrie, and Ajer is anticipating a quick and positive turnaround.

"Now our aim is Aberdeen on Sunday," the 19-year-old Norwegian defender said.

"We will recover well and be ready for that game, 100 per cent.

"Aberdeen have been really good the whole season so it will be a tough game away on Sunday so we need to recover and be 100 per cent ready."

Ajer admits it was another European lesson for him and his Celtic team-mates in St Petersburg, when they had harboured hopes of progression to the last 16.

The former Start defender said: "Of course we travelled with the aim of going through and we felt during this game we could have scored a goal and that's what we needed.

"So it is disappointing to concede three but it is a learning experience.

"It is good to learn at this level but we want to perform better as well. We can learn a lot from this game but we wanted to go through also.

"We didn't start out well and they scored early.

"To be fair they put up a really good set-piece and blocked off me and Jozo (Simunovic) and he (Ivanovic) was free.

"It was difficult but we should do better. It was a tough night."