Wanderers concluded a dismal campaign with a 1-0 defeat at the City Ground with a line-up lacking the likes of Ben Alnwick, Sammy Ameobi and Luca Connell.
The club have just nine senior players contracted to next season and it is understood that Pawel Olkowski has already handed in his notice after going unpaid during March and April. The defender can walk away from the club for free this week and Parkinson has confirmed that other players have now joined the Polish full-back in cancelling their contracts.
Wanderers had to name 10 players involved in their last game against Blackburn Rovers to avoid an EFL fine but the Bolton boss admitted he struggled for volunteers.
“I have been in football for more than 30 years and some of the things that have happened this season are happening to me for the first time,” he told The Bolton News.
“There are some players who have put in their two-week notice, I think some of that has been out in the media, and there are other lads who have offers from elsewhere who, naturally, didn’t want to play.
“We also had some genuine injuries with David Wheater, Jason Lowe, Luke Murphy and Mark Beevers.
“We were left with a bare 18 but I think they showed good character, and that is important.”
Asked if he could have forced players to face Forest, the manager added: “Firstly the lads who put their notices in – if they play and get injured, they are not insured. You have to respect that.
“Those who might move on elsewhere didn’t want to play, which we have had to deal with, but I want to concentrate on those who did, and I thank them for that.”
Wanderers handed a professional debut to Ronan Darcy and a first league appearance for midfielder Jack Earing.
“Given everything that has gone on I am proud of the way the players coped and I think that was recognised by the fans at the end, who were magnificent,” Parkinson added.