Northampton scored three tries before the interval but failed to score after the break and Mallinder was frustrated that they could not build on an excellent display in the opening period of this Aviva Premiership fixture.
"I was slightly disappointed with the second half performance," he said.
"I think in the first half we were very good and dominated the game.
"Our scrum was on top, as well as our driving maul. We defended well and therefore took our opportunities at the right time.
"We talked about doing exactly the same thing in the second half and we didn't do that.
"I'm disappointed with the second half but we got the win and that's important, particularly away from home."
Mallinder also praised Dylan Hartley who was at the heart of Northampton's scrum dominance after returning from injury.
He added: "Dylan in particular is a leader and he leads from the front. He was dominant in that forward effort.
"Mike Haywood's done well over the last few weeks, but Dylan's got that experience and it's good to have him around."
Sale were left to rue their first half display as they found themselves 24 points down at the interval.
Although the Manchester outfit reduced that deficit through Rob Miller and Tommy Taylor tries, they never seriously threatened to come back.
John Mitchell, who has taken over first team affairs from Steve Diamond, described parts of their game as "immature" and will look to improve the set-piece area after being dominated up front.
Mitchell said: "Northampton's forward pack was outstanding in the first half. The determining factor of that period was the lineout drive and I thought they were very effective.
"We never built any pressure or any starting position. In the second half, we showed better character and built some pressure.
"The forwards had a torrid time tonight. We're still very immature as a side and we get frustrated easily, so we've got to learn to become more patient.
"We've got a lot of work to do in the forward area. I thought we had made some growth in the scrum and the lineout, but we got hurt in that area tonight, so we're going to have to spend a lot of time on that going forward."
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