Ireland skipper Brian O'Driscoll will be out for only three to four weeks after a scan delivered a positive diagnosis on his hamstring tear.

O'Driscoll limped off in the 75th minute of Saturday's 16-12 RBS 6 Nations defeat by Wales after being hit by a tackle while stripping the ball on the ground.

It was initially thought the Leinster centre would be sidelined for up to two months but tests revealed the damage was not as severe as first feared.

An Irish Rugby Football Union statement released tonight read: "A scan on Brian O'Driscoll's left hamstring this afternoon has confirmed the presence of a moderate tear.

"The injury is not as bad as was first feared and it is expected that this will prevent him from playing for a period of between three and four weeks."

Leinster currently top the Magners League and the latest news means O'Driscoll will be available for the title run-in — possibly in time for the home clash with Munster on April 12.

The 29-year-old has already been ruled out of Ireland's Six Nations finale against England but will return well before the summer tour to New Zealand and Australia in June.

O'Driscoll's absence has left Ireland without their first-choice centre partnership against England as Gordon D'Arcy is already missing because of a fractured forearm.

Ireland name their team for Twickenham — a happy hunting ground during the last two visits — at lunchtime tomorrow with Shane Horgan expected to plug the gap in midfield.

Horgan looks set to move from right wing to inside centre with Andrew Trimble moving one place down the line.

The make-up of the back-three depends on the availability of Geordan Murphy and Girvan Dempsey, who missed out against Wales because of their respective
Achilles and hip injuries.

If neither recovers in time, exciting Leinster youngster could be in line for a start on the wing.

Eddie O'Sullivan has been urged in some quarters to throw caution to the wind against the World Cup finalists on Saturday by experimenting with a handful of new faces.

On the face of it there may not be much at stake — third and fourth place will be decided — but to finish outside the top three would represent Ireland's worst championship since 1999.