One of Brown's closest friends in the game, Thomson was one of 14 players released by the Easter Road club on Monday after they lost a play-off to Hamilton Academical and were relegated to the Championship.
The Celtic and Scotland captain served his apprenticeship alongside Thomson in the Hibs midfield and said that not playing him enough was "the biggest mistake they made" this season.
Although Thomson was occasionally injured it was clear within weeks of Butcher taking over in November that he would not be an integral part of the team. Thomson played only 10 times under Butcher and started just four games since the turn of the year.
"I couldn't see their relegation coming," said Brown, who left Easter Road for Celtic in 2007. "I don't think anyone could. It's been hard for them and I still can't believe they let Kevin Thomson go.
"Not playing him is the biggest mistake they made. Everyone knows how good a player he is, he went back to the club and played for nothing, got his deal and they were seventh in the league when he was playing week-in, week-out. They would have stayed up if he played more often, 100 per cent.
"It just shows what one or two players can do, especially with his experience. If another team wants him, that's up to them. Hibs have made their bed and he'll get a new club and show what a bad decision this has been.
"It's going to be a tough league with three good teams [Hibs, Rangers and Hearts] going for two places. It's going to be hard."
As disbelief was replaced by determination as the prevailing emotion around Easter Road, Hibs supporters decided at a meeting on Monday night that they would finalise plans this week to reshape the future of their club.
Representatives of as many as 15 supporters groups met former players and other influential figures 24 hours after watching their team concede a two-goal lead from the first leg of the play-off in Hamilton and tumble out of the SPFL Premiership on penalties.
Around 500 fans gathered outside the stadium after the game, with chairman Rod Petrie and Butcher the focus of their fury, and online polls yesterday indicated that 70% of fans were in favour of Butcher's departure and 90% wanted Petrie's removal.
Although relegation has brought their exasperation to a head, it is understood discussions have been taking place behind the scenes among supporters eager for change since Hibs' dismal Scottish Cup defeat by Raith Rovers in February. An announcement on what the fans view as the way forward is now expected at the end of the week.
Those involved were keeping their proposals under wraps yesterday but it is clear that - with Hearts supporters having been successful in saving their club from liquidation, with the promise of running it in future years - Hibs fans are in no mood to take their latest humiliation lying down.
Mike Riley, chairman of the Hibernian Supporters' Association, said: "The meeting went well. We are now checking out two or three things that were talked about and we plan to make an announcement regarding our plans later
Further pressure was placed on Petrie as organisers of Hibs' largest fans forum called for him to quit. Administrators of Hibs.net wrote an open letter to the chairman, who is stepping down as chief executive this week to make way for departing Motherwell CEO Leeann Dempster.
Petrie indicated in the wake of Sunday's defeat that he accepted 'responsibility'
for relegation but insisted: "It would be wrong for me to abdicate that responsibility at this time and walk away, and it would be wrong for the club."
In their correspondence, the owners of Hibs.net made it clear they wanted Petrie
to step down 'forthwith' for the good of the crumbling relationship between boardroom and terrace. It read: "It is with a heavy heart that we, as supporters of Hibernian FC, feel compelled to write this letter. However, in a downward spiral of lows we may well have hit rock bottom as a club.
"As a group, we are all supportive of the decision to bring Leeann Dempster to the club as chief executive, her background suggests reason to be optimistic.
However, this optimism is balanced by the confirmation that Rod Petrie is to continue as chairman, albeit in a non-executive capacity. We have no confidence in
Mr Petrie and feel his continued presence at the club will prevent Ms Dempster properly engaging with the fan base and rebuilding the broken relationship.
"While Rod Petrie remains on the board of Hibernian FC there will be a large section of the support that will distance themselves from the club. He has lost the trust of the vast majority of the support and these fans simply will not return while he remains involved. If nothing else, he should realise this himself and remove himself from the
One of the players unfortunate to find himself cast as a villain in Hibs' downfall was 18-year-old Jason Cummings, who was entrusted with the penalty that ultimately secured Hamilton's promotion when it was saved by Kevin Cuthbert. Cummings had scored both goals in the first leg and
Owain Tudur Jones defended him.
He said: "You could say Jason shouldn't have taken that one, but he felt confident stepping up. He wanted that responsibility and you have to respect that.
"Jason was in tears
in the dressing-room. He has probably gone through the sort of feelings in the past
few days that some
lads don't have in their whole career."