With a place in a preliminary final at stake, Geelong started poorly and trailed by 20 points at the long break.
And the early lull proved very costly when rain turned the game into a slog in the second half.
“If that is not a wake-up call, I don't know what will be, ever,” Thompson said.
“We had a lot of decent players, a lot of good players and just about every player made a contribution at the end.
“But clearly there were way too many people at the start of the game that were not prepared to play and that is not good enough because it is a privilege to be where we are.
“It is not always the same guys that don't always perform well, but I was reasonably upset with some of the guys tonight.”
Thompson was particularly unhappy with Josh Hunt’s early efforts in his battle with Stephen Milne.
The St Kilda small forward continually outsmarted the bigger-bodied Hunt in the second quarter, during which he booted three game-changing goals.
Joel Selwood was another Geelong player who was off his game. Selwood managed only four possessions to half time, although he finished with 19.
“He was bitterly disappointed,” Thompson said. “When he doesn't go well, Joel gets pretty wound up and thinks he is letting everyone else down too and it makes it worse.
“We tried to relax him a few times and asked the players to give him a few touches and he got his game going in the second half and made a contribution.
“I don't think that will happen again with Joel. Next week, he'll be ready to play.”
Thompson was proud of the way his team fought back from a 33-point deficit early in the third quarter.
“The thing about this group is that you never write them off either,” he said.
“They can turn it on when they want and the really important thing for this group and this club is that we play four pretty solid quarters next week against whoever we play.
“That is what we are looking forward to.”
The Cats now meet either Hawthorn or Fremantle in a sudden-death semi-final next Friday.
Key forward James Podsiadly will be available after serving his suspension, while Paul Chapman should be fit despite being crunched by Lenny Hayes early in the loss to the Saints.
“I think he will be sore. I'm not sure what's wrong with it but the fact that he kept playing is a pretty good sign,” Thompson said.
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