Sean O'Brien a Six Nations doubt with shoulder injury

Ireland have been dealt an injury blow ahead of this year's Six Nations after Sean O'Brien sustained a shoulder injury.

The Leinster back row picked up a suspected dislocated shoulder during the team's game against Ulster earlier today.

Such an injury typically results in a three-month absence, but Ireland get their Six Nations campaign underway against Scotland in just five weeks.

O'Brien was part of the successful British & Irish Lions squad that toured Australia in the summer.