"We were pretty peed off to be honest last Tuesday night and we wanted to put things right with a good performance, so it was very good to do that," said O'Brien.
"We wanted to go out and work hard for each other - that was the big thing. We didn't want to turn it into an individual thing. We all wanted to play well, but it was more about our performance."
The Leinster flanker got a rare opportunity to wear the No 7 jersey and was keen to try to put as much pressure on tour captain Sam Warburton ahead of Saturday's vital second Test in Melbourne. Having been the 24th man in Brisbane last weekend for the 23-21 opening Test triumph, he did all he could in his 55 minutes to push his claims.
The management of the breakdown area improved dramatically from the 14-12 defeat to the Brumbies and O'Brien put that down to good preparation.
"It is a bit of a grey area which way the refs are going to ref it. We said we'd deal with that ourselves tonight and just try and pass the ball and take a body out from whatever was in front of us, so it was a bit better certainly than last week," said O'Brien.