Ireland rugby star Chris Henry is expected to make a full recovery from the brain injury that will rule him out of action for at least a number of months.
The 30-year-old Ulster flanker suffered what the IRFU described as an "episode" in which he experienced "weakness" on the morning of the win over South African on November 8 and was ruled out of that game.
Yesterday, the union released a statement that confirmed Henry had suffered "a temporary blockage of a small blood vessel in his brain" which had caused the turn and that the illness would "require further investigation and specialist opinion" as he recovered at home.
There had been rumours that the player had been struck down with something more serious than the initially-reported viral infection, while the diagnosis first circulated by the IRFU was that the player had experienced a severe migraine.
Despite the serious nature of the incident, it is understood that the player's career is not in jeopardy and it is hoped that he will return to the field of play when he has made a full recovery.
He is likely to be out for an estimated three months, but the situation was described as "ongoing" and he will continue to be monitored.
Belfast native Henry has won 16 caps for Ireland since making his debut against Australia in 2010 and was a key component of the team that claimed the Grand Slam last March.
He had been named in the side to face the Springboks, despite sitting out some of Ireland's training sessions after enduring a high number of collisions during Ulster's European games. However, it is not known whether his absences were related to the big hits.
His health scare is the latest in a series of worrying incidents in the professional game, following Henry's Ireland teammate Richardt Strauss's discovery of a hole in his heart during last season.
The South African player took time away from the game and is now back in the Ireland set-up.
The issue of concussion and head injuries continues to be a hot topic in rugby and the IRFU medical team yesterday stood down second row Mike McCarthy for training after he suffered symptoms consistent with concussion during Sunday's win over Georgia.
With the size and pace of players increasing by the season, there are growing fears that the sport is becoming too dangerous.
The International Rugby Board held a discussion about head injuries in London yesterday, where IRB chief medical officer Martin Raftery said the issue was a complex one.
"You can't identify everyone with concussion, there is no magical test out there. What we are trying to do is as best as possible protect those athletes," he said. "We've been able to change the culture so we are getting consistency in the post-game management of those players."
The blockage of a blood vessel in Chris Henry's brain echoes other freak instances where elite athletes have been forced to retire prematurely.
Henry will require further investigation and specialist attention but he will be hopeful that his fate will not echo the likes of Fabrice Muamba and former Ireland international Simon Best.
All decided to quit prematurely after suffering serious health problems.
Bolton Wanderers midfielder Muamba (26) was forced to retire more than two years ago after falling critically ill during a game.
Muamba collapsed on the pitch after suffering a heart attack during his side's FA Cup clash with Tottenham in March 2012.
Simon Best, brother of international rugby player Rory, was also forced in to retirement after suffering with a heart issue.
He had to leave the Irish World Cup squad early in 2007 after he was struck down in Paris while out on a walk, complaining of a lack of feeling down his right side, headaches and difficulties in speaking.
The object of the exercise was to widen the squad (yes, we took winning for granted) and in that it was mission accomplished against Georgia. There were minor blemishes, chiefly in terms of precision and accuracy in finishing, but the overall objective of the mid-series match, by far the least demanding of the three, represented a job done.