With an Aviva Premiership showpiece against Saracens to follow eight days later, Mallinder knows he must manage his squad to give them the best chance of league glory.
But he is also keen to ensure they pick up the European trophy as Saints bid for a stunning double.
Saints were without skipper Dylan Hartley (shoulder), Jamie Elliott (calf) and Ken Pisi (shoulder) for the sensational Premiership play-off semi-final win over Leicester last Friday.
And Mallinder said: “We’re down on the artificial pitch down at Cardiff Arms Park this week and that’s not the best in terms of looking after your body, so we’ve got to be very wise in our selection.
“We’ve got to make sure we get the right team for next week, but last week’s win gives us momentum.”
Mallinder has been managing his squad in recent weeks, resting Courtney Lawes against Wasps in the final game of the regular season and making sure no player plays too often.
And he said: “We’ve got into a position now with our players that we’ve rested them and rotated them throughout the season.
“We’ve not had anyone who has played back-to-back for the last few games, they’ve all been rotated up to now with this in mind.
“We’re not worried about that now. We’ve got two big games and we’ll go out firing to see if we can win them both.”