Harry Mallinder is set to miss Saints' Challenge Cup clash with the Dragons on Friday night due to the knee injury he picked against Clermont Auvergne last weekend.
Mallinder was involved in a huge collision just three minutes into the game at Franklin's Gardens and though he tried to battle on, he was withdrawn just a couple of minutes later.
The 22-year-old was sent for a scan earlier this week and has not trained at all.
And with Saints to announce their team on Thursday, he will not feature in this week's fixture.
"Harry's not been training this week," said Saints attack coach Sam Vesty.
"He's had a scan and we're awaiting the results.
"You'd need to speak to the medics about that one."
Saints are ready to welcome Taqele Naiyaravoro back into the squad after he was rested last week, while Courtney Lawes could also feature at Rodney Parade.
"Taqele has played a lot of rugby recently and he came in, jumped in and hadn't had a massive amount of training base," Vesty said.
"He needed an opportunity to train so we can look after him long term."