Following the narrow defeat to Saracens in the Aviva Premiership last time out, Mallinder has resisted the temptation to rotate his squad for the competition.
Former Newcastle and Toulon back Tom May comes into the centres in the only change in the backs, while England flanker Tom Wood, James Craig and Alex Waller are added to the pack.
It will be a welcome return to action for Wood, who makes his first start since January after suffering a foot injury.
Wood replaces Phil Dowson, who is away with England, while James Downey and Soane Tonga'uiha drop to the bench. Samu Manoa misses out completely.
The Scarlets, themselves, have made just the one change of personnel to their line-up following the 38-10 win over Connacht last time out.
With Jonathan Edwards ruled out through a calf strain, Dominic Day comes into the side. Day's inclusion means Aaron Shingler moves to the blinside, with Josh Turnbull wearing the No.7 shirt.
Northampton: 15 Paul Diggin, 14 Vasily Artemyev, 13 George Pisi, 12 Tom May, 11 Scott Armstrong, 10 Stephen Myler, 9 Martin Roberts, 8 Roger Wilson, 7 Tom Wood, 6 Calum Clark (capt), 5 Christian Day, 4 James Craig, 3 Paul Doran-Jones, 2 Andy Long, 1 Alex Waller.Replacements: 16 Ross McMillan, 17 Soane Tonga'uiha, 18 Tom Mercey, 19 Mark Sorenson, 20 Ben Nutley, 21 Ryan Glynn, 22 Ryan Lamb, 23 James Downey.
Scarlets: 15 Dan Newton, 14 Liam Williams, 13 Gareth Maule (capt), 12 Adam Warren, 11 Andy Fenby, 10 Stephen Jones, 9 Liam Davies, 8 Kieran Murphy, 7 Josh Turnbull, 6 Aaron Shingler, 5 Dominic Day, 4 Lou Reed, 3 Deacon Manu, 2 Emyr Phillips, 1 Rhodri Jones.Replacements: 16 Kirby Myhill, 17 Phil John, 18 Peter Edwards, 19 Sione Timani, 20 Matt Gilbert, 21 Gareth Davies, 22 Nick Reynolds, 23 Iongi Viliame
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