Andy Farrell has confirmed that Caelan Doris is unlikely to return for the remainder of the Six Nations due to concussion symptoms.
The back-rower, who was tipped to be a breakout star against the Springboks by the legendary Sir Ian McGeechan, withdrew before the Wales opener after reporting symptoms that could be associated with a head injury.
Doris then reportedly saw a specialist in Birmingham before Farrell give a worrying update in his press conference.
"Caelan is getting well looked after, seeing the right people, getting the right advice, and making sure he's comfortable on his return to play," Farrell added.
"But we don't intend to see him back anytime soon," added the Ireland coach.
Doris was concussed on his Ireland debut against Scotland a year ago. But he went on to be one of the team's most impressive performers during the autumn campaign, which included a man-of-the-match display against the Scots.
Writing in the Telegraph, the legendary Sir Ian McGeechan has selected a trio of youngsters as potential Lions tour bolters in South Africa in 2021.
3.Caelan Doris (Ireland)
McGeechan's view: "Billy Vunipola is the standout No 8, but I think Doris could really offer something different if a more mobile game is needed. The Irishman is a great lineout jumper and a superb athlete who operates wider out than Vunipola."
Lions odds: 2/1
Our thoughts: Could be on of the breakout stars of the Lions tour. A potential superstar.
2.Ollie Lawrence (England)
McGeechan's view: "With Manu Tuilagi constantly injured and Jamie Roberts absent stage left, the Lions desperately need a forceful ball-carrier in midfield who can take the ball up and get over the gainline early. Ollie Lawrence is a fledgling in Test terms but he's the player best suited to that role, although the excellent Rugby League-style lines run by Scotland's Sam Johnson means he can also fulfil that role too, as he showed at Twickenham two years ago."
McGeechan's view: "There is no substitute for pace, but this potential bolter also glides past would-be tacklers without pausing for breath. Used properly he could wreak havoc, although he is prone to worrying defensive lapses. However, with rock solid campaigners like Anthony Watson, Jonny May and Jack Nowell available, he's a luxury Warren can afford."
Lions odds: 2/1
Our thoughts: The most exciting wide-man around, he could be a breakout star during the 2021 tour