Jim Mallinder reminded Saints that talk is cheap after they fell to a 20-16 defeat at Adams Park.
Scores from Ashley Johnson and Tom Varndell in the space of three second-half minutes helped Wasps end their 10-match losing streak against Northampton.
It was a hugely motivated performance from the home side, whose defence was resolute until Ben Foden broke through late on.
And Mallinder wasn’t surprised by the Wasps spirit, with Saints continually stressing this season would be their hardest due to May’s league title triumph.
“It’s easy to say and we’ve said it all along: everybody’s going to be after us,” said the director of rugby.
“Today it proved that you can’t just talk about it, you’ve got to go out and do it.
“We just weren’t accurate enough in everything we did and you’ve got to give a lot of credit to Wasps because they defended really well.
“It was just little things: getting out of our half, we played too much, they spread the play very well, got off their line and we should have kept it tighter.”
Things were looking good for Saints as they moved into a 9-3 lead 15 minutes into the second half.
George North looked to have extended the advantage as he picked up a Ken Pisi chip to score, but it was ruled out for offside after TMO Geoff Warren intervened.
Mallinder felt that decision was harsh, but admitted his players should have been streetwise enough to stop Wasps getting back in the game.
“I don’t think we played badly but we came up against a very motivated, well-organised Wasps,” he said. “We just weren’t smart enough on the day.
“At 9-3 we deserved that lead. Interested with the George North non-try. From the views I had, it looked even, certainly not in front, but that happens.
“At 9-3, we were in charge of the game and then two really loose bits of play and then to concede from your own kick-off, suddenly you’re up against it.”