Hartson said: “Celtic have a gem in Aiden and he will be a fantastic player in years to come if they hold on to him.
“It will cost a club huge bucks to get McGeady. A player who can pick up the ball 10 yards from his own box, beat four men then pop team-mates through with a lovely little ball is priceless.
“The Champions League is the stage to play on and if he can produce displays consistently at this level what’s to stop a Chelsea paying £20m. Aiden’s better than Shaun Wright-Phillips and Chelsea paid plenty to get him from Manchester City.
“McGeady has the lot – pace, skill, vision, the ability to take players on. I hope Celtic can keep him because he’s a special talent.”