Saturday night's upset 24-point elimination final loss to Port Adelaide left a grim-faced Buckley talking about the need for his team to evolve quickly or be left behind.
Collingwood started the season as strong top-four candidates, but finished the home-and-away games in sixth place.
While the elimination final was an absorbing duel, the Magpies were unable to kick clear of Port when they had momentum.
"We didn't believe that our season was going to end here, but it just shows how tough this competition is," he said.
"If we have any person or anyone or have any thoughts at all that we need to cling on to what we've had, well, then this is the last blow that lets that go and you need to keep evolving.
"You need to be hungry, hard on each other, be prepared to continually improve whether you finish first or you finish last.
"You need improvement because otherwise the competition goes past you."
It could be the last game for veteran Alan Didak, who came on in the second half and helped set up two goals for the 'Pies at the start of the last term.
Star Dale Thomas is yet to commit to a new deal and he is about to become a free agent.
Buckley would not comment on list management but he said the club had to ask hard questions.
"You've got to ask if we're making the right decisions in regard to culture and in regards to environment, personnel, game plan, coaching staff etc.
"You've got to consistently and continually ask yourself that question and when you come off a performance like that, it gets asked pretty strongly."