11 points from Jonathan Sexton and a Keith Earls try was enough for Ireland to get past a stubborn Italy side by 16 points to nine.
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Joe Schmidt made 11 changes from the 44-10 win over Romania, as Ireland named a much stronger starting XV. Only Simon Zebo, Keith Earls, Tommy Bowe and Jamie Heaslip retained their places, with Bowe given the chance to build on his impressive showing at Wembley and other key players returning.
Italy and Jacques Brunel also made a few alterations following their last pool game. Andrea Manici, Matias Aguero, Simone Favaro and Michele Capagnaro all came into the fold following the win against Canada, in a bid to spring a surprise against one of the tournament favourites.
Both sides trade early kicks
The Italians were dealt a blow early on when Tommaso Benvenuti was called upon to replace Gonzalo Garcia. The centre was taken off with what looked like a fairly innocuous knee injury. Despite the personnel problems, Italy were seeing plenty of the ball but came up against a resolute Irish defence, though a silly penalty stopped them in a promising position.
A lovely break by Jonathan Sexton would provide the first points of the game after some quick hands from Peter O'Mahony. His run brought about a penalty and Sexton's routine kick gave Schmidt's side an early advantage.
It would be another needless intervention that brought Italy onto the scoreboard. Jamie Heaslip was off his feet and Tommasso Allan, formerly Tommy of Scotland, made no mistake from the 20-metre line to level the scores.
Earls cross to give Ireland breathing space
That gave the Italians hope but it was soon wiped away. Keith Earls was the man to cross over beside the posts after Ireland had won the ball from Italy's line-out. Iain Henderson and Paul O'Connell made excellent ground before Sexton produced a subtle reverse pass to Robbie Henshaw. He picked out fellow centre Earls, and Sexton kicked the resulting conversion to give Ireland a 10-3 lead.
Allan was back on the board a few minutes later, as a 35-metre attempt sailed through the posts. Sergio Parisse had missed an excellent two-on-one situation to play through his backs earlier in the move, and an even better opportunity was missed in the aftermath. A line-out right on Ireland's goal-line flew well-over their players, straight into Dave Kearney's hands.
Contrasting fortunes at the end of the half
The dying embers of the half saw Sexton miss a long-range penalty before Ireland wasted a great chance to extend their lead. Italy repelled an double-digit phase drive and then a knock-on from Conor Murray let Brunel's men off the hook. Earls broke free in the final play of the half, but his pass was just out of Zebo's reach, brining an end to an entertaining 40 minutes.
Ireland's line speed went up hugely in the first few plays of the second half and that put Allan under huge pressure. The 10 had a kick charged down, though O'Mahony was tasked with making a vital tackle to stop Joshua Furno from crossing. He just managed to bring Furno's feet into touch, in what was another strong start by the Italians.
Ireland close out the game to seal the win
Allan did convert another tough kick to bring the score to within one, as Italy continued to be defiant across all areas of the pitch. The game was looking very similar to the Six Nations clash earlier in the year, though Ireland had much more of a cushion in that match.
Just as it was becoming tight and tense, Sexton slotted two penalties to put a converted try between the teams again. In the meantime, both sides made their changes to the front row. The Italians looked particularly down-hearted as they came off, knowing that their chance of an upset had slipped away in just a few phases of play.
No sooner had Allan departed that Italy had a chance at three points, but the inexperienced Carlo Canna's kick didn't have enough legs to creep over. Peter O'Mahony's game came to an end sooner that he would have liked, after Jérôme Garcès - rather harshly - penalised him for not using his arms in a ruck.
Sexton then missed the chance to put the result beyond any doubt with a last minute penalty. It did not come back to bite the Irish, who held on for the win and now have a showdown with France to avoid New Zealand in the quarters. Italy, on the other hand, were valiant and gave a great account of themselves.