Republic of Ireland midfielder Robbie Brady lost consciousness during Thursday's 1-0 win in a World Cup qualifier against Georgia, manager Martin O'Neill confirmed.
The win came at a cost as Brady was carried from the field on a stretcher wearing an oxygen mask after an ugly 76th-minute clash of heads with defender Solomon Kverkvelia.
The manager of Brady: "He was out cold for a while. He's come back round again and the doctors and physios are pretty pleased with him since he was carried off.
"He 's obviously gone off at this minute [to hospital] and naturally I am hoping the lad will be fine. He's as brave as a lion, great courage obviously and a fine player, and he started to get into it in the second half himself."
The concussion protocol could mean he will miss the game in Moldova on Sunday, where Jeff Hendrick will be suspended after picking up a second yellow card of the campaign.
O'Neill also said he was a relieved man after seeing his side snatched three priceless points after a tense battle with Georgia.
Seamus Coleman's senior first international goal secured a 1-0 Group D victory at the Aviva Stadium, but there was concern both on and off the pitch as Ireland laboured for long periods.
"The players knew themselves that they weren't at it in the first half, and these games are so important. It's not as if we have 38 games and we can put things right after four or five. We have 10 games to play," O'Neill said.
"Every match is important and [on Thursday night], the performance was not so good, but winning the game was vitally important."
Georgia were unfortunate not to take a 37th-minute lead when first striker Levan Mchedlidze's header came back off the bar and then skipper Guram Kashia's follow-up struck the upright.
Their fortunes took a further turn for the worse after the break when Coleman's surging run to goal was aided in no small part by deflections off defenders Kverkvelia and Kashia.
O'Neill said: "Just the drive and determination that he showed to get that distance, then he got a wee bit of luck to score the goal -- Coleman was terrific for us."
If O'Neill wore a smile as he turned his attention to Moldova, opposite number Vladimir Weiss, who had spoken in the run-up of the bad luck he had witnessed while reviewing his team's performances before taking up the reins, was left to curse misfortune once again.
However, he admitted that they had paid a heavy price for one mistake.
"When you don't score goals, you cannot take points," Weiss said. "We showed good quality in the first half. We had three chances to score.
"I hope in the future this team can play better and better and better. This is not easy, three or four months making a new team.
"We played well against Austria and we have played well against Ireland, but we have zero points. This is football.
"It's not only unlucky. It is unlucky, but as I have said from the first day, we cannot make one mistake."
Meanwhile, O'Neill was nonplussed by rumours that midfielder Harry Arter, who has withdrawn from the squad through injury, could opt instead to represent England having yet to make a competitive appearance for Ireland.
He said: "I have no idea. He hasn't played a competitive game for us and the choice is entirely with the player. It's news to me."