Brian O'Driscoll believes that Japan’s scouting of Ireland’s long-standing weaknesses led to their shock 19-12 win in the Rugby World Cup.

The former World Player of the Year joined Off The Ball this afternoon to discuss where the game was won and lost for Ireland, and a result that leaves them in a relatively sorry state for the remainder of the tournament.

In particular, it was the time spend assessing opposition weaknesses that the Japanese did superlatively, according to O'Driscoll.

"Jamie Joseph said that they have been preparing for this game for two-and-a-half years, since this group stage was announced.

"I thought the scouting they did was absolutely excellent. The Achilles heel of Ireland has always been them getting narrow in defence.

"Watching their pod runners in particular taking the ball and running the ball outside, severing the defence not close to the ruck, but far away, made sure that Ireland piled numbers around the corner.

"That does two things - it tires the legs of the players having to work harder, and if they decide to be lazy and not do it, then it means that they will be short of numbers on that side."

It was the execution as much as the preparation that impressed O'Driscoll yesterday.

"I have to say, huge credit to Japan for the manner in which they scouted Ireland's frailties because they certainly exposed them and they managed to match them up front for physicality," said O'Driscoll.

"When it came to trying to stretch them, the pressure that they put on us in attack and defence squeezed the life out of us and didn't allow us to play our game in any shape or form."

O'Driscoll rejected any prevailing thought that the Ireland players were somehow negligent in their approach based on a sense of complacency.

"I think that they really thought way more than some of us," he said of the Irish approach.

"I think the players thought that this was nearly the bigger game than the Scottish game, from a few weeks out. Playing the host nation - a team with a good bit of promise - they certainly didn't take this for granted.

"It wasn't a case that that performance was sprung on them, I think they thought this was going to be a real dogfight of a test match."

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