Celtic captain Callum McGregor has told Sky Sports News that Wilfried Nancy's desire to change "too much too soon" was his downfall.
The Frenchman was sacked after just 33 days as manager, with their 3-1 defeat to Rangers his final match of a disastrous reign.
Under Nancy, Celtic lost six out of eight games and twice missed the chance to move level with Hearts at the top of the Premiership.
He immediately scrapped the Hoops' favoured 4-3-3 formation to use his favoured 3-4-3. McGregor insists they were always going to struggle with such drastic change.
"For me, it was just a little bit too much too soon in terms of that change and quite a big change away from what the team had been," the captain said ahead of Sunday's Premiership clash with Hearts, live on Sky Sports.
"To go from a team that is super aggressive on the front foot for 10 plus years, playing a certain way and then you bring in the nuance of the league and playing in Scotland, my belief is that you get as much pressure on the ball as much as you can and try and press the game as high as you can and actually eliminates a lot of the defending that you have to do in terms of box defending.
"Not to say that it can't work, but I think everybody is well aware of the time and no pre-season and so many games, so many important games.
"Really, really tough situation to come in and have a game every three days where you're almost learning in the game and we all know that trying to learn in this environment is probably the harshest environment that you can have.
"When you take away that confidence, everybody starts to struggle with that.
"You have to go to the pitch and have confidence and belief in yourself and, ultimately, when you lose games that does waver.
"We're all human beings at the end of the day, so it does affect you."
'Still in the conversation'
Celtic trail Premiership leaders Hearts by six points in the title race, but a winning run during Martin O'Neill's two spells as interim boss has kept them in contention.
"There's been so many negative stories going about this season. There actually is so much positive to look forward to, so much to play for and the players have drawn a line under it," the 32-year-old added.
"I think now for everyone externally as well we have to draw a line under it and move forward because if we keep dwelling on it, we aren't going to achieve what it is we want to achieve.
"The players are at peace with that and we know we've put ourselves in a difficult position, but still in the conversation with a huge game to come on Sunday."
