"To be honest with you I'd be pretty critical of it", he said.
"If we had a little more structure during the weeks, and more of an attack gameplan, driven way earlier in the tour, I think we could have won 3-0", O'Brien said. I think we probably should have won the tour and we probably should have won it comfortably enough.
"We did almost a similar thing in the last week".
Speaking at a sponsorship event for his provincial side Leinster, O'Brien told the Irish Examiner how backs coach Rob Howley struggled to coach the best of Great Britain and Ireland to take on the best team in the world.
"If I was being critical of any coach it would be the fact that I think Rob struggled with the group in terms of his attributes of trying to get stuff across whereas Johnny and Owen drove everything the second week, for instance, in our attack and had a better plan in place".
"On the first week (of the first Test), we had a triple (session) day, (the) lads' legs were heavy on the Thursday and we were playing the All Blacks on Saturday".
The series was deemed a success from a Lions perspective when you consider they defeated the All Blacks and denied them a series victory when everyone had diminished their chances before the tour began.
O'Brien was forced from the field at halftime of the third test draw after coming off second best from a Jerome Kaino clear-out.
The Irish forward said that he raised his concerns regarding the squad's preparation with coaching staff during the tour. "We had said it, at the time, and they pulled back a bit". Maybe less is more sometimes on a tour like that.
"We just need to be short and sharp'".
O'Brien scored a classic try in the first game but he said the tour was "probably one that got away from us".