Luther Burrell is set to miss Saints’ game at Castres on Saturday after suffering a concussion setback.
Burrell was knocked unconscious in the defeat at Saracens on September 17, but he went through the protocols and returned to action at Harlequins on October 8.
Saints lost that game at The Stoop 20-9 and Burrell, who played the full 80 minutes, then did not feel 100 per cent at training two days later.
The centre missed last Saturday’s 16-14 Champions Cup win against Montpellier and is set to be sidelined for this weekend’s clash with Castres.
“Luther’s going through the return to play protocol,” said Saints assistant coach Alan Dickens.
“He had a bit of a setback so he’s going through the protocol as we speak.”
And when asked whether Burrell had come back too soon, Dickens replied: “He was okay and it was after the game, on the Monday, that he felt a bit (unwell), so he started the process again.”
Dylan Hartley has not played since the September 11 win at Bristol due to a back injury, but the England captain looks set to return to action this weekend.
Dickens said: “Dylan trained fully last week, he’s trained fully this week and it depends how he reacts.
“He’s there or thereabouts, it’s not confirmed but he’s trained fully.”
And Courtney Lawes is also likely to be available for Saints after missing the win against Montpellier with a knee problem.
“Courtney’s back, he’s trained fully,” Dickens confirmed.