"I am really proud of the lads. That was a great performance and some of the young guys - Peter O'Mahony and Tommy O'Donnell in particular - were phenomenal, particularly in the 15 minute period after half-time," said O'Connell.
"We were completely written off, so to come away from home and win a quarter-final is a very special feeling. That performance has always been there and it was jut a case of bringing it out.
"The players work incredibly hard and there are many more performances like that in them waiting to come out. We never discussed playing the way we did in the end, we just had momentum and good feel about what we were doing.
"The maul worked well for us, our kicking game was outstanding and we were getting good information from the sidelines. There wasn't a lot said at half-time, but we got the bounce of the ball at the start of the second half, a few decisions went our way and a number of players put up their hands.
"Casey Laulau had some good carries, Peter O'Mahony stole one of their five man line-outs, our choke tackles were excellent and we played a very good pressure game. The plan was do to whatever was required of us at any particular moment and that's what we did.
"The maul went well for us and we did things that put them under pressure and built pressure on them. This is a very important day for this young group of guys.
"There have been people doubting them for a while and it was very important they got a day like this to realise their hard work is worth it. I am really happy their hard work has paid off."