Mallinder's men leaked four tries at home against Heineken Cup conquerors the Scarlets a week ago.
Saints have a proverbial mountain to climb in terms of reaching the Heineken knockout phase, but victory over Franklin's Gardens visitors Saracens (kick-off 5pm) could lift them into the Premiership title play-off zone.
"We have to be a lot better against Saracens, pure and simple," Mallinder said.
"Although our discipline was excellent against the Scarlets and we finished off our chances, we gifted them too many tries and turned the ball over far too many times.
"Saracens have a team full of quality players who will punish our mistakes."
Scrum-half Lee Dickson makes his 100th appearance for Northampton as Saints look to rediscover a winning formula after successive Heineken Cup defeats against Munster and the Scarlets. England's Ben Foden returns at full-back, with George Pisi switching to midfield, while there is also a start for prop Paul Doran-Jones.
Fly-half Charlie Hodgson misses the trip to Franklin's Gardens because of a knee injury suffered during Saracens' Heineken Cup defeat against Biarritz last Saturday. Owen Farrell deputises, with Chris Wyles and Brad Barritt teaming up in midfield. Hooker John Smit makes his Premiership debut, continuing instead of a suspended Schalk Brits.
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