Joe Schmidt lamented the poor start Ireland made in the opening minutes of the quarter-final clash with Argentina in Cardiff on Sunday.
Los Pumas took advantage of some lacklustre Irish defence to score a brace of early tries which saw them run out to a 17-0 lead after just 13 minutes.
While Ireland battled back to within three points, the Argentines turned on the class at the back end of the match and ran in two more tries to seal victory.
"We just did not get the start that we needed, particularly with a group low on experience," quipped the New Zealander.
"The confidence got dented a little bit but I was incredibly proud of the way they fought their way back. We had a kick which could have drawn us level and might have allowed us to kick on.
"It wasn't to be and really when you try a little too hard at the end you get loose and, with the speed merchants Argentina have, they finished off another couple of tries and that exacerbated things.
"It reflected the tour de force we have seen demonstrated by the southern hemisphere teams. We were desperate not to be part of what happened in Saturday's matches."