Geelong coach Mark Thompson has warned his men not to bother turning up for a sudden death AFL semi-final unless they are prepared to be desperate from the start.

While the crucial moment of Friday night's 12.11 (83) to 11.13 (79) qualifying final loss to St Kilda was the debatable late free kick which cost his side a comeback win, Thompson said it should never have reached that stage.

The Cats were 20 points down at halftime, a deficit which stretched to 33 early in the third quarter, before steaming home in driving rain, and pressing constantly in a last term in which they outscored the Saints 1.7 to 1.0.

Thompson was severely disappointed his players did not start the match with the same attitude they showed at the end, and told them the same approach next week would mean a straight sets finals exit.

"I said 'The next game we play, we better make sure that if you're not prepared to play well from the start then don't turn up and play for this club,' and I meant it," Thompson said.

"You see the boys jumping in late in the game when they were a chance to win and be really desperate, we want people to be desperate at the start of the match."

He expected the players to respond at the MCG on Friday night, against the winner of Saturday's Subiaco clash between Fremantle and Hawthorn.

"If that's not a wake-up call, I don't know what would be, ever," he said.

"... We got it right towards the end, but clearly there were way too many people at the start of the game that were not in the mood to play.

"And that's not good enough, because this is a privilege to be where we are."

Thompson acknowledged midfielder Joel Selwood, who had just four first-half touches, was one of the disappointing players early, and said backman Josh Hunt too easily gave up three goals in six minutes to Saints forward Stephen Milne.

Key defenders Matthew Scarlett and Harry Taylor also started slowly, with their opponents Justin Koschitzke and Nick Riewoldt dominating the first quarter, although Scarlett kept Koschitzke touch-less after quarter-time.

Thompson was publicly guarded about the free kick which cost skipper Cameron Ling what would have been a lead-changing goal with 61 seconds to play.

As Ling's shot rolled through and Cats celebrated, forward Cameron Mooney was penalised for falling into St Kilda's James Gwilt's back in a tackle, a decision that was probably technically correct, but could easily have gone unpaid.

"You write whatever you want to write, and write the truth about that last incident, that's all I'll say," Thompson said.

"I don't want to risk any fines, I'm not going to say anything about the umpires, I'm sorry, I can't."

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