Sean Cronin is set to miss the whole of the Six Nations after a scan revealed his hamstring injury is worse than first thought.

It’s now emerged the hooker suffered a high-grade hamstring tear in Leinster’s PRO12 victory over Zebre 10 days ago.

Cronin has been ruled out of action for 10 weeks as a result, with Ireland’s campaign wrapped up in nine weeks. His absence leaves Ireland short of cover for captain Rory Best at hooker.

Ireland’s first Six Nations match is away to Scotland on Saturday, February 4.

Leinster coach Stuart Lancaster said on rbs6nations.com: “It’s quite a significant hamstring injury.

“It’s a real shame for him as he’s actually playing great rugby but it’s a good opportunity for us to get him right and make sure we don’t get a recurrence of this because it must be hugely frustrating for him.

“He’s got himself into great form and now he’ll miss the RBS 6 Nations. He went to push-off and accelerate around the corner and saw it go. He’s deeply disappointed but he’ll be back a better player.”