O’Brien’s final fate hangs in the balance
The flanker was seen to strike opposite number Yannick Nyanga after the Toulouse forward had obstructed him in the run-up to Louis Picamoles’ try shortly after half time during Saturday’s thriller at Lansdowne Road.
It appeared O’Brien was swinging merely to free himself from the Frenchman’s illegal grip but Paul O’Connell received a four-week ban earlier this season for a similar reaction against the Ospreys’ Jonathan Thomas, for which he also received a red card.