Knights' skipper Kalyn Ponga and teammate Kurt Mann raised serious questions about the club's culture after they were filmed being escorted out of a toilet cubicle at a Newcastle pub on Saturday night, while both are sidelined through injury.
That issue was further compounded when centre Bradman Best and winger Enari Tuala were stood down for being late to a team bus.
O'Brien said it was on him and his players to own the criticism of their culture and move forward, with their side still reeling from their 6-15 season.
"We've got some people that need to grow up really quickly and become really professional over this summer," he told reporters.
"That's kind of the only thing that we can do now to get this club back to where it needs to get to.
"Naturally anytime there's a spotlight on off-field behaviour it's disappointing ... it's not a good look for our club and the players understand that.
"They've taken responsibility and it's about me helping educate them and driving standards that will make sure we're heading in the right direction."
Captain Ponga has drawn the bulk of the heat with his professionalism questioned, with calls for him to be stripped of his leadership as he fails to justify a $1 million-per-season pay packet.
Ponga's father told media earlier this week his son had been drinking when he was filmed exiting the cubicle despite being on a break for multiple concussions, and while the Knights were playing in Brisbane.
O'Brien admitted Ponga would need to spend the off-season repairing his relationship with teammates.
"He's a young captain, I gave him the captaincy, so it's my responsibility that we help him grow in that area and I'm confident that we can learn from this and move forward," he said.
"He's a young bloke, I don't want to make excuses for him, he doesn't want that.
"For Kalyn, it's about helping the team prepare and trying to win back a little bit of respect and trust from teammates."
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