Wayne Bennett revealed Kevin Brown was substituted in England's Rugby League World Cup quarter-final win over Papua New Guinea after a team-mate in the stands saw footage of his head knock on social media.
Warrington Wolves half-back Brown took a heavy blow to the head in a tackle during the first half of his side's 30-6 victory, but initially played on despite briefly appearing dazed.
In his post-match news conference, England head coach Bennett explained the chain of events that led to Brown subsequently being withdrawn as the opening period came to an end.
"Kevin's good," said Bennett. "The doctor, when he went on the field, didn't see the incident because there was no replay board - it wasn't working. So he went on, Kevin assured him he was fine and he had no major symptoms that suggested he had been knocked out.
"Nearing half-time, one of our players was on social media, one of the players not playing, and up came a replay of the incident. At that stage, no one had seen the incident. He showed the doctor.
"The last thing Kevin wanted to do was come off. He had no symptoms at all, but because of what you could see on the replay, that he was knocked out for maybe a second [we brought him off].
"In Kevin's mind, he was stunned, he didn't feel he was knocked out, but it looked bad enough for the league doctor and our doctor to say it was a category one [incident] and they took him straight off the field."
Next up for England, whose performance against PNG was described by Bennett as "the good, the bad and the ugly", is a semi-final clash with Tonga.
Jason Taumalolo and Andrew Fifita sensationally turned their backs on New Zealand and Australia respectively to join Tonga's squad ahead of the tournament.
Bennett has no problem with either player turning out for the tier-two nation, but believes the process surrounding international eligibility needs to be examined.
"I didn't speak publicly about it when it happened, but the game has to look at it and we have to treat the fans with a lot more respect than we did with this issue," he added.
"Whatever country they want to play for, that's fine with me. But we need to have a look at that and how we can make that better for everybody concerned.
"It wasn't what the game needed with the World Cup about to start. It was [making] headlines for two or three days.
"The boys, in my opinion, are entitled to play for who they want to play for, but we've just got to have better guidelines around it."