The Easter Road club confirmed that 11 squad members would not have their deals renewed, while three more; Sunderland's Duncan Watmore, Notts County striker Danny Haynes and Arsenal youngster Daniel Boateng, have returned to their clubs after ineffectual loan spells.
Unconfirmed reports have also circulated suggesting other players still with agreements in place for next season, including captain Liam Craig - who is rumoured to be heading back to former club St Johnstone - have been told they are free to find new clubs during the close season.
Terry Butcher, the manager, held meetings with his out-of-contract players just hours after Sunday's desperate penalty-kicks defeat by Hamilton Academical in a play-off final in which Hibs came within 90 seconds of safety before succumbing to relegation.
All three first-team goalkeepers - Williams, Sean Murdoch and Paul Grant - were freed, while the player-coach Alan Maybury, the midfielder Tom Taiwo and the winger Paul Cairney joined McPake and Thomson in departing. The list was completed by youngsters Bradley Donaldson, David Gold and Dean Horribine.
The futures of such as defensive pair Michael Nelson and Ryan McGivern, the versatile Lewis Stevenson, the misfiring striker James Collins and the experienced forward Paul Heffernan have also been called into question amid suggestions of a pay cut in the Championship.
McPake left the club's East Mains training ground with a parting shot aimed at Butcher and his assistant Maurice Malpas after failing to play a single game under the pair, despite claiming to have returned to fitness following a back operation.
He said: "The manager has told me that I'll not be part of his plans. I'm gutted. I loved playing for this football club. We had some good, and some very bad, times as well. But I'm more disappointed I never got the chance to help the club stay in the division. The blame lies with the players as we got the club relegated but you can't look entirely at the players.
"Sunday was a devastating day for everybody. It is a fantastic football club and to be relegated is heartbreaking, not just for the players but for everyone behind the scenes that I know it's going to affect. Everybody's dejected and gutted we went down.
"But we had plenty of chances. We had one win in 19 games, which is relegation form, and we've only ourselves to blame, as a club. But you can't just level it all at the players. I'm 100%, I've been training for 10 weeks. Could I have played a part? Definitely. That's not to say I would have made a difference, but I was fit enough."
Thomson departed yesterday's meetings also with a grievance over his lack of game time under Butcher after he made just eight appearances since the new manager's arrival in November.
The former Scotland cap, who had returned to the international set-up under the previous manager Pat Fenlon earlier in the season, said: "I'm obviously disappointed. It's hard, everybody knows how much I love the club. But unfortunately the manager's got a different opinion to a lot of people, so I have to respect that and I will now be looking for a new job.
"Did I expect it? I think so. It's only natural the way he's been with me over the last six or seven months since he came in. "I would like to think I tried my best to repay him when I did get in the team and tried to put on some good performances - unfortunately Sunday wasn't one of them.
"I think it's hard to judge somebody on one game of football. But at the end of the day it's his opinion, he's the manager, he needs to pick his team and unfortunately I'm not going to be a part of that."
Thomson missed the first spot-kick in the penalty shoot-out against Hamilton and revealed his bitter disappointment at not being able to save the club he supported as a boy. "It was devastating. I was as hurt as all the other Hibs fans; I'm a Hibs fan. It breaks my heart to see the club in the situation they are in and to be a part of that. I wish I could have come on and changed the game. I tried my best to get a hold of the ball and calm us down a wee bit, but I think, unfortunately, from the first minute to the last we were second best to Hamilton.
"I don't think if the manager could have made six or seven changes it would have made much of a difference. Over the course of the season, the table doesn't lie, it's the way it is. Over the two [play-off] games I don't think we were good enough and over the 38 games we weren't good enough. It's been a slide for over four or five months now and a lot of people saw it coming."