Ken Pisi will fill the void left by George North in Saints’ clash with Leinster at Franklin’s Gardens on Friday night (7.45pm).
North has been stood down by Saints, who sent the Wales star for an independent assessment earlier in the week.
The club insist he has no concussion symptoms after the collision with Leicester Tigers wing Adam Thompstone at Welford Road last weekend.
And North has said that it is a neck problem that is troubling him rather than a head injury, but every precaution is now being taken.
Pisi was the player who replaced North while the 24-year-old was off the field for a head injury assessment (HIA) last weekend, and the Samoan gets the nod this week.
Nic Groom also comes in, at scrum-half, while England duo Courtney Lawes and Tom Wood are straight back in the side after returning from international Duty.
Dylan Hartley and Teimana Harrison are on the bench as Mike Haywood and Jamie Gibson have been performing well in their absence.
Kieran Brookes and Calum Clark are serving the final week of their suspensions, while Christian Day remains out after taking a blow to the head against Newcastle Falcons.
Leinster have named a formidable side, with centre Robbie Henshaw and full-back Rob Kearney passed fit.
Adam Byrne makes his Champions Cup debut as he starts on the right wing.
Saints: Foden; K Pisi, Burrell, Hanrahan, Elliott; Myler, Groom; A Waller, Haywood, Hill; Paterson, Lawes; Gibson, Wood (c), Picamoles.
Replacements: Hartley, E Waller, Denman, Ratuniyarawa, Harrison, Kessell, G Pisi, Tuala.
Leinster: R Kearney; A Byrne, Ringrose, Henshaw, Nacewa (c); Carbery, L McGrath; J McGrath, Cronin, Furlong; Toner, Triggs; O’Brien, van der Flier, Heaslip.
Replacements: Tracy, Healy, Bent, Ruddock, Conan, Gibson-Park, R Byrne, O’Loughlin.