George North's coach at Northampton has said it was "unfortunate" that Wales staff failed to spot a blow to the head the wing suffered against England.
North has been left out of Sunday's squad to face Scotland, but has not suffered any concussion symptoms.
Wales said their staff did not spot the second of two blows to the head.
"Sometimes it happens," said Saints boss Jim Mallinder. "You're watching the game and you quickly move on from an incident."
He added to BBC Radio Northampton: "It's very unfortunate that the medical and coaching staff missed the incident."
|Wales in the 2015 Six Nations|
|Friday, 6 February: Wales 16-21 England|
|Sunday, 15 February: v Scotland, Murrayfield|
|Saturday, 28 February: v France, Paris|
|Saturday, 14 March: v Ireland, Cardiff|
|Saturday, 21 March: v Italy, Rome|
North, 22, was taken off the field for an assessment after an initial kick to the head in Friday's 21-16 defeat, but a subsequent collision, which seemed to briefly knock him unconscious, was missed by Wales staff.
The Welsh Rugby Union were not sanctioned by World Rugby for the oversight, but television replays could be used in the future to assist medical personnel.
Having already suffered a concussion in November, North has been given an extended recovery period by Wales, and has been replaced by Liam Williams in the starting XV for the trip to Murrayfield (KO 15:00 GMT).
"We're pleased he has had no ill effects after the game and is making a good recovery," said Mallinder.
"Of course you can miss it, particularly if the player gets up and recovers quickly.
"But if someone is reacting strangely you have people who can look back for you and see what's happened.
"Five, 10, 20 years ago that player would have been pushed back out and be playing. The protocols are much better now."