"You would never expect to come to Northampton and get a result like that. The way we played in the first 20 minutes was very, very good and they couldn't live with the tempo at that point," said O'Connor.
"That performance with the ball has been coming for a couple of weeks and the players need to enjoy it. We knew it was there and we have worked really hard. We knew that with a bit more time in the saddle that performance was just around the corner.
"They clawed their way into it a bit, but we were very, very good in those opening 20 minutes. We spoke about it earlier in the week that the Saints always like to start big, make a statement early on and get some dominance. But some of the execution in the first 20 minutes was outstanding."
Leinster, who had beaten Saints in the 2011 Heineken Cup final at the Millennium Stadium, played so well they scored their opening try within two minutes of the start, had bagged a bonus point in 36 minutes and led 26-0 at the break. Not only that, they scored first in the second a half as well.
"We were pretty comfortable with what we had done in the first half, but we didn't want to let ourselves down, let them back into it in the second half and turn it into an arm wrestle. We probably left a few tries out there, which isn't a bad thing ahead of next week," said O'Connor.
"That's half the job done and we have to ensure we bring the same intensity next week. That's a quality performance against a very good side, but we don't want to get lost in it - its cup rugby and every game and every point matters."
Having coached at Leicester Tigers before heading to Dublin O'Connor knows more than most what it takes to win at Franklin's Gardens. He also now knows how much the Heineken Cup means to teams like Leinster.
"It's a real shame if it isn't in the same format next season. If we can put some of the egos aside, and look at what's in the best interests of the game, then we should be able to put it back together," he added.