Ex-Leicester City boss Brendan Rodgers admits they could have signed Ademola Lookman.
The forward netted a stunning hat trick in the Europa League final for Atalanta on Wednesday.
Lookman took the Italian side to their first trophy, beating Bayer Leverkusen 3-0 on the night.
Speaking to talkSPORT, Celtic boss Rodgers said: What a professional he is, how he looks after himself, the extra work he does in training.
Those goals that he scored, he practices those after training. He'd always do extra finishing.
His professionalism was unbelievable and the only sad part for us was at the end of that season, we had a clause where we could have bought him for 14 million.
But if you think back to that summer we couldn't sign any players and then one of my guys that I worked closely with here at Celtic and at Leicester was a guy called Lee Congerton and Lee was by then the general manager of Atalanta.
When he knew that we weren't able to take him, he took him then out to Atalanta and he's done absolutely brilliant there."