Sean O'Brien's afternoon came to a premature end after the Ireland flanker suffered what appeared to be a concussion midway through the first half against England.
The injury came at the end of a trademark charge at the England defence, and the tackle looked innocuous enough, but when the ruck cleared and O'Brien attempted to get back to his feet, the Leinster man was unable to do so.
Team doctor Eanna Falvey rushed to his assistance and immediately signalled a head injury. O'Brien was replaced by Munster's Tommy O'Donnell.
https://www.youtube.com/watch?v=0bUNNUk5F4c
