The 33-year-old is out of contract at the end of the season and has turned down a new deal amid interest from the Major Soccer League in the United States and a bid to take him to Australia by Western Melbourne.
Forrest, however, revealed Brown’s team-mates firmly hope he will decide to extend a stay at Celtic which began in 2007 when he made a £4.5 million move from Hibernian.
Brown’s performance as Celtic suffered a first Old Firm defeat of manager Brendan Rodgers’ reign had many again questioning whether he still has what it takes, but Forrest insisted the former Scotland skipper should never be written off.
He said: “Everyone has their opinions but inside the club, the players and staff, everyone knows how influential he is on and off the park.
“Right since I came through he has always been the same and even now he could be the fittest he has ever been. It’s incredible how long he has done it and he still has a few years left in him.”
Brown’s influence on the pitch in almost 500 appearances in the hoops has been apparent for all to see but, revealed Forrest, few outwith the Celtic changing room appreciate just what a key figure he is within the club.
Forrest himself found Brown his biggest ally when he was finding the going tough but, he insisted, the midfielder has always been there for any of his team-mates.
He said: “Broony has always been in and about it every day, training games as well. I think he likes players first and foremost who work hard, give it everything and I think you earn his respect for doing that.
“And obviously when you go out on to the park you have to produce as well. But I think for Broony everyone at the club knows just how big he is and definitely everyone wants him to stay.
“Ever since I have been here there have been different changing rooms and he has always been there, kept everyone together. You maybe hear different stories from different teams but Broony is massive in that part as well that people maybe don’t see.
“He’s great with the young boys, different nationalities, as well which I don’t think many people have got. Even when you go into the international set-up as well he just earns respect from everyone and that’s just credit to his nature. Off the park as well I think everyone respects him.
“I think anyone who talks to him outside football, when he does interviews, you can tell what type of character he is. He’s great with young boys and new signings as well. He’s invaluable I would say.
“For me he has always been the captain, the main man and if he did leave for me it definitely would be strange.”
Like the rest of his team-mates, Forrest admitted he’s anxious to discover just how Brown is thinking but appreciates such a big decision is very much a private matter, one for the individual and his family to make.
He said: “He obviously has options and I think the manager has come out and said he’s earned the respect. It’s maybe a big decision and one he’s not going to make overnight. Whatever he does everyone will back him.
“Everyone knows he has been linked in the past six months but as I said, it’s up to him but I hope he stays.
“I do not think any of the boys would ask him. They would just leave it to reading stuff like yourselves. I don’t know if he will stay, I hope he does.”
Forrest also appreciates that someone like Brown wouldn’t want to hang around simply to be a bit-part player, saying: “He wants to play every game, every minute. When he got injured, he came back and when you see him in training he is as fit as ever. I think he knows himself that he can still do it for another couple of years and for a player like that, we definitely need him in the team. I can only say for me, I hope he stays because he has a lot to offer for the team on and off the park.”
While Brown weighs up his options, Rodgers has made three signings in as many days as he seeks to guide Celtic to yet another title, the Glasgow side having gone into their winter training camp in Dubai ahead of rivals Rangers only on goal difference with Kilmarnock a point behind the Old Firm duo.
Oliver Burke, Timothy Weah and Vakoum Issouf Bayo have come in as the Celtic manager has strengthened his squad and their arrivals will bring greater competition for places and, in the case of on-loan winger Burke, perhaps even put Forrest’s own position under threat.
The 27-year-old, though, insisted he was simply relishing that challenge. He said: “Celtic is a massive club and always looking to strengthen and help the squad. I think a couple of new faces in will boost everyone and hopefully kick everyone on.
“You know they are always going to look to bring in new players and players to better the team and the squad so you know you will have to always be on your toes whether you are playing or not playing.
“They are always going to get better so you have to keep doing what you are doing to stay in the team and that’s what I am doing
“Competition for places is always a good thing, everybody wants to play and works hard in training and that’s what the manager wants.
“You have confidence in your own ability but when Celtic sign players they are always good players so you need to keep working hard on your game to stay in the team.”