Saints skipper Dylan Hartley has been ruled out of Saturday’s Aviva Premiership game at London Irish with a back injury.
Mike Haywood comes in for the England hooker, who sustained the problem in the 31-24 victory against Bath at Franklin’s Gardens last weekend.
Alex Waller also takes his place in the front row, replacing Alex Corbisiero, who is out until the new year after having shoulder surgery.
Christian Day misses out, with Courtney Lawes returning in his place after missing the Bath game with a shoulder knock sustained in the success at Newcastle six days earlier.
Lee Dickson and Kahn Fotuali’i continue their rotation at scrum-half, with the former coming in for the latter, while Jon Fisher continues in the back row with Tom Wood still out with a back injury.
Irish coach Smith has made one change to his team from the one that saw off Leicester Tigers last weekend.
Ireland International Tomás O’Leary starts at scrum half, with Darren Allinson coming onto the bench. Scott Steele misses the match through injury.
Saints: Foden; K Pisi, G Pisi, Burrell, North; Myler, L Dickson; A Waller, Haywood, Ma’afu; Lawes, Craig; Clark, Fisher, Manoa.
Replacements: McMillan, E Waller, Denman, Dowson, Harrison, Fotuali’i, Hooley, Wilson.
London Irish: Fenby; Lewington, Mulchrone, Geraghty, Short; Noakes, O’Leary; Court, Paice, Aulika, Skivington, Sinclair, Low, Cowan, Narraway
Replacements: Stevens, Parr, Halavatau, Leo, Guest, Allinson, Sheridan, Ojo