Six Nations fears for Jonathan Sexton
For the second successive Six Nations, Johnny Sexton will come into the tournament under the cloud of concussion after he was forced off with yet another head injury during the first half of Leinster's record European defeat to Wasps on Saturday.
The Ireland squad report for duty at their Carton House base tonight to begin preparations for their three-in-a-row bid, but their key player will train away from the rest of the team for the first few days at least as he goes through the 'return to play protocols'.
The IRFU will issue an injury update this lunch-time, but that is likely to be light on detail.
Sexton's case is especially sensitive given his history of head injuries. The 30-year-old was stood down from all rugby for 12 weeks of last season by French neurosurgeon Jean-Francois Cherman after suffering a series of concussions in a short space of time and missed Ireland's Championship opener against Italy before returning against France.
The out-half has not suffered a confirmed concussion since that injury, but had his World Cup campaign cut short with an adductor muscle injury.
The latest incident occurred in the eighth minute of the clash at the Ricoh Arena, as Sexton looked to support Noel Reid in the tackle of Brendan Macken but collided head-to-head with his former Leinster team-mate.
He received treatment, but actually got up to tackle Macken again as play continued before being helped off for a head injury assessment (HIA). Sexton failed that test, meaning he could not return to the play, and Cathal Marsh finished out the game.
"Johnny just got a head knock so we didn't want to risk him going back out there. He's up and about in the dressing-room being assessed so he'll follow the usual 'return to play' protocols," head coach Leo Cullen said after the game.
"Those guys are in (Ireland) camp next week, but he looked okay in the dressing-room there."
Today, he will begin the return to play protocols and the earliest Sexton would be allowed take contact would be Thursday if he shows no fresh symptoms of concussion.
The out-half's case is complicated by his history of head injuries and it remains to be seen if he will be treated differently from other cases as a result.
Since Sexton's last concussion in November 2014, two of his Ireland colleagues, Kevin McLaughlin and Declan Fitzpatrick, have retired from rugby, while England's Mike Brown and Wales' George North have both had long-term spells out of the game due to head injuries.
While his primary focus will be on getting back into training for the Six Nations, there must surely be doubts in the back of his mind about the long-term impact of these blows on his health.
Although he is seen as a strong defender, the nature of out-half play means that he will continually be targeted by opposition forwards, and word appears to have gone around that Sexton can be got at and he is regularly slow to get up from big collisions during games.
After the retirement of Paul O'Connell and Brian O'Driscoll, Sexton is Ireland's marquee man along with Sean O'Brien and teams know that stopping him is key to stopping the Six Nations champions. He rarely gets through 80 minutes for province or country.
Unfortunately, he is well used to the routine he will go through this week.
"It can vary," Sexton said of his reaction to repeated head injuries in 2014.
"You can get a bang on the head and be perfect a minute later (or) you can struggle for a couple of days. Even if they are small they have to be looked after; that's the big improvement. Before, the small ones were just brushed aside. Now they are looking after us better, which is a great thing.
"There are different degrees of concussion; the doctors will ask you for your symptoms and it might just be the case where you rest for a couple of days and wait for things to calm down and then you're good to go again; or it could be a few weeks.
"The symptoms afterwards. . . if you have a bit of memory loss, nausea, headaches it is more severe. If you are perfect 24 hours later then it is not as severe. They are the markers you have to go through. Three or four days after a suspected concussion you have to make sure you're good to go.
"It's great that we are looking after players now, that they are not making the same mistakes that were made previously."
The injury presents a major concern for Joe Schmidt as he get his hands on his players for just the second time since the World Cup exit ahead of the Championship opener against Wales on Sunday week.
The New Zealander is often unhappy with the lack of preparation time afforded him and now he will begin preparations for the Aviva Stadium game without his first-choice out-half.
That is the best-case scenario. Deep down, Schmidt must be concerned that the player, with whom he has a close relationship, has suffered yet another injury to his head and will also worry that his history may delay a return.
What Schmidt's Plan B will be remains to be seen. Last season, he went for Ian Keatley for the opener in Rome due to Paddy Jackson's injury and Ian Madigan's lack of opportunities at out-half for Leinster.
At the World Cup, Madigan stepped in for Sexton in the quarter-final after playing brilliantly against France, but the 26-year-old was one of several players who never got to grips with the Pumas. Jackson is back in the squad and playing well for Ulster, while Madigan has since committed his long-term future to Bordeaux, who he will join in the summer.
Although the IRFU don't have an official policy on overseas players, Schmidt has only ever picked one man who plied his trade outside Ireland and that was Sexton. He may see Jackson as his long-term option.
Firstly, he will assess the health of his first-choice No 10 - and Marty Moore, who limped out of Saturday's game with a hamstring injury - and hope for the best when the doctors report to him today.
The return to play protocols
Day One: Complete rest
Day Two: Light cardiovascular work on an exercise bike
Day Three: If no symptoms, the player can begin moderate running
Day Four: If symptom free, the player can do some strength and conditioning work
Day Five: If the player does not show any after-effects, he can return to full contact training
The player is closely monitored at each stage and if he shows any signs of concussion again he goes back to stage one and begins again