George North is set to miss Saints' Champions Cup clash with Leinster on Friday night after being referred to an independent specialist.
The Wales star was involved in an incident with Leicester Tigers wing Adam Thompstone in the 16th minute of Saints' defeat at Welford Road last weekend.
North landed awkwardly after going up to collect a bouncing ball and flying over Thompstone's shoulder.
Some pundits felt North had been knocked unconscious as he lay motionless on the turf, but the player has since revealed that he wasn't moving because he was worried about his neck.
He received medical attention before heading off for a Head Injury Assessment (HIA), returning to the field eight minutes later and playing the remainder of the match.
After the game, Saints released a statement, stressing that 'player safety is the club's primary concern' and insisting that World Rugby protocols were followed.
North has not trained since and Saints released an update on Tuesday afternoon, saying the player had been sent to an independent expert.
"As at every Premiership match, the Saints' medical team has access to video footage to be used to assist the pitchside assessment of injuries," the statement read.
"It is important to note this video footage is not always the full range of replay angles available to the TV viewing audience at home.
"George was fully assessed by the doctor away from the pitch using the established protocols and processes, and passed fit to return to play.
"As with all such injuries, if evidence suggesting a loss of consciousness had been available to the medical team at the time of assessment, George would not have been allowed to return to the field of play.
"All rugby supporters will no doubt be delighted to learn that George remains well.
"Nevertheless, Northampton Saints continues to place player welfare as its number one priority, and is referring George to an independent expert as part of the club's ongoing assessment process and George will be stood down from play until this process is complete."
When asked about the matter at club's media day on Tuesday, forwards coach Dorian West said: "George had got no symptoms and he's living his life as normal - that's where we're at.
"He's got no symptoms and he's cracking on.
"I've not looked at him, examined him, I don't know.
"He probably won't play this week - there's a statement that has been made by the club - and he's living his life as normal.
"It's Tuesday and we don't have to name our team until Thursday.
"He hasn't trained today, which was the first training day of the week.
"The medical team deal with it and we've got a really good record of looking after players and making sure we do the right thing by them.
"George is going to get checked over by a specialist and we'll see how it goes."