The scrum is viewed as Irelands Achilles heel with Wales coach Gareth Jenkins admitting the Triple Crown holders front row will be targeted at the Millennium Stadium on Sunday.

Destructive props Chris Horsman and Gethin Jenkins are expected to trouble John Hayes and Marcus Horan while the selection of Alix Popham and Ryan Jones in the back row adds beef.

OSullivan believes Wales will only look to play their famed running game once their
forward assault has broken Ireland up-front.

Wales know they are good at moving the ball so thats what they will try to do, he said.

Thats been their trademark for the last few years and they have been very successful at it.

But if you look at their selection then its evident they believe they will have to soften up our pack first.

Theres no secret what their plan will be tomorrow - to stamp their authority on the match with their pack.

Once they feel they have softened us up enough they will look to move the ball away.
The battle lines have been drawn between the two packs but if Wales get the ball they will run with it.

Hayes and Horans problems in the scrum during Munsters Heineken Cup defeat by Leicester last month has only served to underline Irelands greatest shortcoming.

Wales are expected to gain an advantage in the front row and OSullivan admits scrummaging has been a key area in training this week.

We always scrum live on the week of a Test game - thats why we have more people in camp, he said.

We havent put a huge amount of effort into it, weve just been more selective about what were doing.

Theres an opinion that scrummaging his just a lot grunt and hard work.

Theres an element of that but if you do that theres a danger youll leave your best energy on the training pitch.

But we have paid a fair bit of attention to scrummaging.

What Ireland lack in the scrum they make up for in other areas, namely the midfield where Brian ODriscoll and Gordon DArcy are the most formidable centre partnership in Test rugby.

But in James Hook, 21, they face a rising star who has enjoyed a sensational start to his international career and OSullivan is a keen admirer of the Ospreys back.

The exciting thing about Hook is that hes hit the ground running since winning his first cap, he said.

He seems to tick all the boxes as a rugby player. The most important box is his temperament because hes shown extraordinary composure since hes come on the scene.

Hes a player who has become an important cog in the Wales machine very quickly.