You perform or you don't play. 

That's what North Melbourne defender Scott Thompson has gathered from coach Brad Scott's decision to drop three players, headlined by experienced forward Lindsay Thomas, for Saturday night's season-defining clash with Geelong at Etihad Stadium. 

"The players understand the coaches are going to pull the trigger if you're not in good form or you're not playing the team structure," Thompson said on the eve of his 150th game for North. 

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"The message is clear and we're all on notice. That's good – the players like that and you perform, or you don't play." 

Majak Daw and Trent Dumont have also been omitted, while important defender Lachlan Hansen (hip) goes out of the side through injury.

Ben Brown, Ryan Bastinac, Taylor Garner and Aaron Mullett are North's four inclusions for the game against the Cats.

Thompson said the coaches have challenged Thomas to be switched on defensively for the entire contest.

"He's one of the best forward pressure players in the game so if he keeps working on that and making sure he does it the whole time, consistently, he'll be straight back in," Thompson said.

"He's one of our best players. We love him in the team and we hope he can come straight back in."

Thompson said there were no excuses for poor performances as the 12th-placed Kangaroos look to keep their finals hopes alive against the 10th-placed Cats.

"We haven't really worried about where they are on the ladder, it's more about where we're on the ladder," he said.

"It's a big game. We've dropped plenty of games so far in this season and if we don't start winning, finals are out for us."

Thompson nominated Jonathan Brown and Brendan Fevola as his toughest opponents when he was starting out his career, although Lance Franklin and Nick Riewoldt feature prominently on that list now.