The black, green and gold were beaten 55-26 at cinch Stadium at Franklin’s Gardens, but picked up a try bonus point to stay fourth in the Gallagher Premiership standings.
And Saints must bounce back quickly against a Sale side who lost 27-14 at Worcester Warriors last time out.
“The real frustration comes from the fact that everything is built up towards the derby weekend, and we started the game as poorly as we did,” Dingwall said.
“That’s the main reflection from the game; we weren’t at the races for the first 35 minutes, and to be honest we fed their gameplan in terms of the kicking strategy.
“In a derby match, which is a game built on emotion, to not come out and fire a few shots in the first half is extremely disappointing, but I don’t think there’s as big a gulf between the two sides as the scoreline suggested at all – some of our mistakes and the game opening up at the end flattered them slightly.
“We did show that when we put our game out there on the pitch, as we did at the start of the second half, we are every bit as good as (Leicester) are.”
“That’s what it has to look like for us for long periods; we need to all be pulling in the same direction for 80 minutes rather than in short bursts.
“The boys are going to have to front up to this result, that’s the reality for this week.
"We can only look to respond, and we take on Sale this weekend – who are a similar side to Leicester in the sense that they are going to by physical.
“We’ll need to improve up front to win that game, and make the defeat to Tigers a turning point where we excel from here.
“There are lessons to learn quickly; it starts from winning collisions and then getting our launch and tempo right. Whenever we do that, teams struggle to live with us, so that’s really important.”