Ireland boss Andy Farrell has been hit with another injury blow after Leinster wing Jimmy O'Brien was ruled out for "a number of months" with a neck injury.
The 27-year-old last played in their Investec Champions Cup win over Sale on 16 December but is believed to have picked up the injury during the Munster game at the end of November.
He was subsequently withdrawn from the Ulster game on 1 January after pulling up in the captain's run.
"Jimmy O’Brien has picked up a neck injury and will be unavailable for a number of months," the province said in a statement.
The news comes hours after Connacht confirmed that Mack Hansen would miss three to four months due to a shoulder injury suffered against Munster on New Year’s Day.
The Ireland wing (above) was due to undergo surgery today in Dublin.
O’Brien, who has eight Ireland caps, came on as a replacement in the World Cup quarter-final defeat to New Zealand.
Fellow Leinster and Ireland wing James Lowe has not played since that game in October but is now back in the mix.
"Yeah, James is back training with us," senior coach Jacques Nienaber told RTÉ Sport.
"This would be his second week, today was his third [session] so if everything goes well and he gets selected it would be good to have him back."
Jacob Stockdale, Jordan Larmour, Calvin Nash and Robert Baloucoune are among those who could come into Six Nations contention.
Farrell is expected to name an extended panel next week for the championship, which starts away to France on Friday 2 February.
Meanwhile, flanker Martin Moloney has suffered a bicep injury that will keep him out of action for "a number of months", while back row Alex Soroka picked up a foot injury and won’t be available for Leinster’s Champions Cup match against Stade Francais at the Aviva Stadium on Saturday.
Captain James Ryan, who was withdrawn shortly before the URC loss to Ulster on New Year’s Day, will be assessed during the week.
Charlie Ngatai (calf), Cormac Foley (shoulder), Ross Byrne (arm) and Jamie Osborne (shoulder) continue rehab.
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