Celtic manager Ronny Deila was recently quoted as saying by The Glasgow Evening Times that Forrest has turned down a new contract offer from the Scottish Premiership giants.
This means that the 24-year-old Scotland international winger could leave Celtic Park at the end of the season.
Hay understands Forrest’s decision, but he has suggsted that Celtic will not miss the winger.
“I know some supporters are unhappy with him, they don’t like to see anyone knocking back the club, but Forrest’s Celtic career has probably come to a natural end,” the former Celtic manager wrote in The Glasgow Evening Times.
“Four seasons ago he was Young Player of the Year, he scored in big Champions League matches, a cup final and got into the Scotland squad. That all seems a long time ago.
“He hasn’t even been a regular this season and his form overall has been disappointing, although as always with him there are some great performances in there.”
“Forrest has won plenty with Celtic and played his part in the club’s recent success,” added Hay. “But would he play such a big role in the coming years? I’m not so sure about that.”
According to The Daily Mail, Premier League side Norwich City and Championship outfit Queens Park Rangers are interested in signing Forrest in the summer transfer window.
Celtic are at the top of the Scottish Premiership table at the moment with 62 points from 27 matches.
Ronny Deila’s side are six points clear of Aberdeen, who are currently second in the standings and are their main title challengers.