Farrell has made an encouraging start to Test rugby, assisting Jonny Wilkinson in marshalling Englands backline in the RBS 6 Nations victories over Scotland and Italy.

OSullivan believes Farrells presence reduces the pressure on Wilkinson but knows he faces his toughest assignment yet when he meets Brian ODriscoll and Gordon DArcy at Croke Park.

He said: Jonny and Andy are two different players but they both have a lot of gravitas and leadership.

Theyve played at the highest level and performed. Its an interesting dynamic between them.

Whats been beneficial for England is that Farrell has emerged as a talisman in the middle of the pitch and taken some responsibility from Wilkinson.

That eases the burden on Jonny. Theyve both slotted in at first receiver and Brian Ashton is obviously keen for Farrell to shoulder more responsibility.

It will be interesting at the very least to see how the midfields do on Saturday. Im looking forward to it.

Ashton was appointed Englands new head coach in December and has overseen a successful start to the Six Nations, lifting the gloom that accompanied the world champions slump.

OSullivan believes Ashton, who had a brief and uncelebrated spell as Ireland boss in 1997, is a canny operator who will get England fired-up for their Croke Park debut.

He said: You can see Brian Ashtons stamp on the game already. Hes trying to get the ball into the outside channels and trying to create quick ruck ball, creating mis-matches.

He has the right personnel around him. Hes smart enough to play the games that suit his players.

Theres always a trade off between the game you want to play and the one you can play.

The team are fairly comfortable with their game plan and know that if they implement their it properly, they will give us a tough day.

Skipper Brian ODriscoll has been restored to the team after recovering from a hamstring strain but the fitness of scrum-half Peter Stringer will be checked again on Thursday.

The Munster veteran is struggling with a fractured hand and if he fails to pull through, Ulsters Isaac Boss will continue in the number nine jersey.

OSullivan said: The situation with Peter is encouraging at the moment.

His progress slowed down this week but he had a workout on Monday and there has been no adverse reaction to it so far.

Well wait until tomorrow before taking another look at it.