The St Patrick's Day celebrations were muted as the Irish slumped to the most demoralising defeat of Declan Kidney's three-year reign. A worrying period for Irish rugby will find little comfort in the looming three-Test summer series against New Zealand, but O'Brien refuses to accept fears that the squad's best days have passed.
"That was pretty embarrassing and we're not too pleased about it," the European player of the year said. "It's a hard loss to take and that was the most disappointed I've been in an Ireland jersey."
Two victories and a draw represented their worst Six Nations since 2008, when a return of four points cost Kidney's predecessor Eddie O'Sullivan his job.
Desperately missing talismen Brian O'Driscoll and Paul O'Connell, they were smashed to pieces by an English side that obliterated their scrum.
"We're must take a long look at ourselves over the next couple of months until we come back together for the tour. But I wouldn't agree that this is a team on the slide. We've shown what we can do at times and it's just getting that consistency.
"If we play to our potential week-in, week-out, we'll be a force to be reckoned with."
Ireland's misery extended beyond the result thanks to a relentless demolition job on their scrum that was painful to watch at times.
The neck injury sustained in the opening set piece by tighthead Mike Ross, who soldiered on for half an hour before being substituted, was offered by Kidney as an explanation for England's dominance.