The Hawks were a long way off the pace in their 67-point belting at the Gabba last month, which at the time cast serious doubts over their flag credentials.
But they have bounced back and more than repaired a damaged reputation, soaring into a home preliminary final with a stunning upset of minor premiers Fremantle.
Hawthorn host the Lions at the MCG on Saturday with a grand final spot up for grabs and the recent drubbing still fresh in their minds.
"That was a good wake-up call for us - we were nowhere near good enough," Mitchell said on Thursday.
"We finished that game with some mirror-looking and saying, 'OK, what do we need to do as a collective and individually to make sure that we're ready to compete against this level of intensity?'.
"They brought it on that night and we weren't up to it. I said after that game that I doubt if we played them again it would be the same, and we'll see if that's true."
Mitchell is confident Hawthorn are now much better placed to take it up to the all-conquering Lions, who have reached the past three grand finals for two premierships.
"Sometimes little things slip that you might not notice until they punch you in the face - and that night (in round 22), that's exactly what happened," Mitchell said.
"We've righted some wrongs since then and whether we're up to the standard of what this team will bring, we think we are if we produce our best."
Hawthorn's intensity was the key feature of their win over Fremantle, who couldn't handle the heat in their qualifying final.
Mitchell has rammed home the point to his players this week that the pressure will go up another level again in the preliminary final.
"It's part of my job and the coaching staff's job to tell them what is going to matter in this game," Mitchell said.
"Pressure and intensity around the ball, ball-handling and tackling - all of those basics that we've been told about since we were kids - are going to be big on the biggest stage."
Hawthorn were beaten by eventual runners-up Geelong in a preliminary final last season, after losing a semi-final in 2024.
They face a Brisbane side laden with finals experience, gearing up for a fifth consecutive preliminary final.
"History would say that you have to lose some games to be a bit more battle hardened," Mitchell said.
"Even Brisbane, they've been there. They've been in prelims consistently over the last few years and grand finals as well, but before that they had some losses.
"We've hopefully been through that period, but they're small margins in a lot of these games."
Mitchell opted against recalling fit-again Ned Reeves to partner first-choice ruckman Lloyd Meek, who faces a huge task against Brisbane pair Sam Draper and Darcy Fort.
Meek will be supported by key forward Mabior Chol and part-timer Josh Weddle, with the Hawks naming an unchanged line-up.
Brisbane are also unchanged after their semi-final thumping of Adelaide last week.
Mitchell expects Lions midfielder Josh Dunkley to run with Hawks co-captain Jai Newcombe.
"Dunks has been amazing for a long time and I'm glad he gets some credit from the outside world," Mitchell said.
"He's a player who you watch as a coach and you love what he does. You imagine that they would, (but) I don't like it that much.
"He plays a fantastic team role for them and he's a very important player. I suspect he'll go to Jai, but time will tell."
