Cardiff ran in seven tries as Saints went down 43-13 at the Arms Park with the opening clash against Worcester next Sunday.
But Saints were up against two teams as Cardiff substituted their whole outfit at the break and the likes of fresh internationals Ceri Sweeney, Martyn Williams and Tom Shanklin ran in four tries in a 12-minute second-half burst.
Mallinder was pleased to give his squad more match practice and with the final pre-season clash against Italians Treviso tomorrow will be hoping for a rousing send off from the rest of his squad in front of the Franklin's Gardens faithful.
"It was a really good, useful exercise," said Mallinder. "It is a pre-season game and what we wanted to do this weekend was give as much of our squad game time as we could.
"We struggled early on in the second half when we conceded three or four tries when they brought on a completely fresh team and we had Paul Diggin in the sin-bin. We didn't cope with it very well over that period. It was really positive how we regrouped and had a really strong final 20-minute period."
Saints' two tries came from Alex Rae, which gave the visitors an early lead, and senior academy No. 8 Rob Milligan.
Mallinder was also pleased with a first-half defensive display that saw two tries conceded as Cardiff dominated.
"I think our first-half performance was really good," said Mallinder. "I think defensively we were really sound, we worked really hard for each other. Plus I thought some of the young lads did really well out there."

Full match report in today's Chron