The Hawks trailed by just six points at halftime in the Saturday twilight fixture, but were unable to stop their energetic opponents running over the top in the second half.
The Demons piled on a dozen goals after the main break in their emphatic 18.12 (120) to 12.9 (81) victory at the MCG.
"It's a challenge to be able to put your finger on it, but I would say that it's an outlier performance for this group," Hawks coach Mitchell said.
"It's been a long time since you would have to say that we have been genuinely out-worked in a game.
"It's very rare that I would've questioned that part of our group, but I just thought that they were a bit too good for us today.
"It's back to the drawing board. We lick our wounds and go again."
Hawthorn lost spearhead Jack Gunston, key defender Tom Barrass and Conor Nash to injuries in the build-up to the Melbourne clash and had to negotiate travel home from Perth.
But Mitchell refused to use the hurdles as excuses for a second straight loss, which meant the Hawks (6-3-1) slipped to sixth on the ladder.
"We've still got the same number of jumpers out there as they do and our injury list across the course of the season has been pretty light-on," Mitchell said.
"So we're in good hands from a medical point of view.
"We had a couple this week, we might get one or two of them back next week, but I think other teams have been tested from a depth point of view much more than we have been so far."
Hawthorn won centre clearances in the first quarter against Melbourne, but were overpowered by ruck star Max Gawn and the Demons' midfield from that point.
They still narrowly won the inside-50 count, but couldn't make the most of their chances in attack.
"We found great ways to not score from good entries, and they were really potent going the other way," Mitchell said.
"That's been a bit of a pattern for us where we aren't able to get scores-per-entry as high as we'd like over the last few weeks, but before that it had been really strong."
Hawthorn have just five days to recover, hosting Adelaide in Launceston on Thursday night.
Mitchell expects leading goal-kicker Gunston (foot) to recover in time to play against one of his former clubs.
"Of course someone like Jack will help us coming back, but that's not to say that we need to rely on one player," Mitchell said.Â
"We need to play system-based footy."
14°C