Kilmarnock manager Lee Clark rued the "crazy decision" by Conrad Balatoni which led to keeper Jamie MacDonald's red card and defeat at Inverness.
The relegation-threatened side led 1-0 when Balatoni's "blind" back-pass saw MacDonald sent off for pulling down Ross Draper and Greg Tansey's penalty.
"I could understand if he was facing the keeper but he just turned and hit it blind when he was facing up-field.
"It was a crazy decision and it has hurt us," Clark told BBC Scotland.
"There were so many knock-on effects from it. We gave away a penalty, allowed them back into the game and lost a keeper who has probably been the best in the division this season.
"We then made another error from a set-piece and when the players keep making errors, you have to think they are not learning the process, and you have to change the personnel."
Defeat leaves Kilmarnock seven points adrift of Hamilton, who they face next Saturday, after Accies' later win at Dundee United.
"We might have made it more difficult for ourselves now but we have to keep fighting," Clark added.
"We will be fine. We have to re-group and next week (against Hamilton) was always going to be a huge game anyway. It is no different now."
'We need to get a standing ovation' - Hughes
Caley Thistle boss John Hughes hailed a "massive result" for his side, which lifted them 11 points clear of Kilmarnock with only four games left.
"The sending-off certainly swung it in our favour," he acknowledged.
"You feel for Kilmarnock and the player who made the mistake. They got hit with a triple whammy there. But it was good to capitalise on that.
"I sensed a bit of trepidation and tension in our game. Our preparation was perfect but we struggled to produce what we have been working on in training.
"We have been so slow out of the traps. I don't know if it's because of our position but it is like any performer going onto the stage.
"You are either magnificent and get a standing ovation, or you fluff your lines. When we get on that stage, we need to get a standing ovation. You can't have any anxiety in your mind-set, or it will stop you enjoying it and playing your best.
"But sometimes you need to dig deep and all credit to the boys for that. I have seen us play better and quicker but it is a massive result for us."