DUBLIN (AP) — Italy's no-ruck tactic bamboozled England in the Six Nations but Ireland flanker Sean O'Brien believes his side would have had no such problems.

Masterminded by coach Conor O'Shea and defense coach Brendan Venter, Italy's ploy of not contesting rucks flummoxed England on Sunday at Twickenham.

Expecting to put 50 points on the board at least, England actually trailed 10-5 at halftime to a team it has never lost to.

The Azzurri's strategy of refusing to compete for possession after a tackle so confused England that flanker James Haskell was heard to ask referee Roman Poite: "On the ruck thing, what do we need to do for it to be a ruck?"

Poite replied: "I can't say, I'm the referee, I'm not a coach."

England ultimately won 36-15 but coach Eddie Jones was annoyed, and said the laws must be reviewed.

O'Brien, however, said Ireland was aware that no ruck means no offside line, and would have known straight away how to combat it.

"I certainly would have known the rules around it anyway," he said on Monday. "England dealt with it in the end but in fairness to the Italians they were very clever and smart in the way they went about their game plan.

"So you have to hand it to them, too, but you have to adapt to those situations if they arise, and it took England a little bit to do that. But they got the result they needed in the end."

O'Shea has vigorously defended the tactic, and despite Jones' complaints, not everyone appeared to want to condemn Italy.

In his Daily Mail column, England's 2003 Rugby World Cup-winning coach, Clive Woodward, wrote: "I totally support Italy and their use of their innovative and inspired tactics at Twickenham on Sunday.

"It was one of those rare moments in test rugby that, as a former coach and player, make you sit bolt upright in your seat and think, 'Wow, this is different, this is new.' What on earth do England do next?'"

England host Scotland next week.