The Republic of Ireland international, who will go head-to-head with his Celtic successor in qualifying for Euro 2016, recalls setting eyes on the teenage Forrest when he was promoted to train with the Parkhead first-team squad and believes only a series of nagging injuries have prevented him from following him to the Barclays Premier League.
"I was able to monitor his progress when I was in Russia because I kept tabs on Celtic," said the Everton midfielder. "I watched as many games as I could and I would also go online to read match reports and articles. James has been unlucky with injuries and, if it hadn't been for those, he'd already be at the next stage of his career.
"Right now he needs to get back the momentum of playing every week because he definitely has the potential to play at the highest level.
"At Celtic there were always a lot of younger boys training with the senior players, boys who have been playing for the reserves and who are supposed to be the next big thing.
"But James was the only one I ever thought had a chance of making it. He came in and he looked like a first-team player straight away. Where other youngsters would be overawed he would get on the ball and beat players and just play his normal game.
"He's played a lot of games for Celtic but I think there's still a good bit more to come from him. He has the quality and all the tools you need to become a top player.
"We're different kinds of players; his game is based more on pace, although he's technically good as well, while I'm more inclined to beat opponents with a trick or a little feint. There's a possibility he could have moved on already but for those injuries. Clubs were watching him and if he had carried on playing as well as he had been, then the sky would have been the limit."
*Aiden McGeady was speaking at the launch of the PFA Scotland player of the year awards 2014, sponsored by Cheque Centre.