The Crows on Friday are seeking to rapidly come to terms with being pitched into sudden-death mode after their 24-point loss to Collingwood.
The Pies booked an MCG preliminary final while minor premiers Adelaide will host a knockout semi-final next weekend against the winner of Saturday's eliminator between GWS and Hawthorn.
"Obviously pretty frustrated, pretty disappointed, with the result," O'Brien told reporters on Friday.
"We obviously went in with high hopes to book a home prelim, we weren't able to do that.
"So right now I am still in that probably upset, angry mode.
"As a competitor, you're pretty angry just losing a game - especially a high-stakes game like that, against a team you've had history with and a lot of close games with.
"It probably just burns a little bit at the moment."
The Crows, in the club's first final since 2017, were overwhelmed by a ferocious Collingwood, who produced a game-breaking 15 minutes in the third quarter.
The Pies booted five consecutive goals in a stunning quarter-hour that effectively secured victory.
"Their pressure was really good, it was definitely elevated from what we've had (in the home-and-away season)," O'Brien said.
"And we weren't able to handle that and combat that, weren't able to use the ball going forward as well as we'd like, and played into their hands."
Adelaide coach Matthew Nicks held a hasty review with his players after the match ahead of an in-depth examination on Saturday.
"The big theme was intercept marks against ... it was 28 against," O'Brien said.
"You're not going to win too many games of footy with that.
"That was largely with our composure with the ball really, we were just banging it on the boot straight to their numbers a lot of the time.
"That was the first theme that came up.
"And then a little bit of, just some moments at the start of that third quarter, they rushed us and we weren't able to halt momentum quick enough."
While O'Brien recorded nine more hit-outs than his opponent Darcy Cameron, Adelaide's midfield failed to fire.
Skipper Jordan Dawson (19 disposals) was subdued, and fellow on-ballers James Peatling (nine touches) and Sam Berry (12) had little impact.
Midfielder Jake Soligo's 21 disposals were at 38 per cent efficiency, and winger Isaac Cumming had just seven possessions for the match.
"We all probably had moments on the night where we didn't do our best and didn't execute under pressure," O'Brien said.
"And that's probably the whole team thing ... we all had moments we'd certainly like to have again.
"Lucky for us, we have earned the second chance throughout the year through the way we played.
"We're back at home next week and able to rectify that."
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