"I'm hugely frustrated as we didn't really play," admitted Director of Rugby Ruddock.
"Northampton pressurised us in the lineout and they made things difficult for us. In the tackle area they put a lot of pressure on us and made that difficult all game. We gave away a lot of penalties and weren't accurate and we need to look at that.
"I have some concerns about our ability in the tackle area - which I shouldn't have because we really focussed on that but after seeing the game I have. I also have some concerns over the interpretation in terms of the directive in the tackle area and how it will impact on overall rugby.
"But in fairness to Saints, they deserved their victory and took their chances. My frustrations are that only once in the game did we generate some genuine quick ball and we scored a try of it.
"There is a lot of unfinished business from this team that we didn't see today."
Worcester lost flanker Tom Wood in the second half to the sin-bin and Northampton immediately struck with the game's first try though replacement hooker Dylan Hartley.
Ruddock admitted it had been a turning point in the match but refused to dwell on it as the key component in defeat.
"It was a significant moment, but we are never going to challenge it because if the referee deems that is what should happen then obviously we take it," he said.
"We will look at it in the cold light of day on the video, but my feeling was that there was a similar penalty later on where a hand was used and Northampton were penalised. There is an argument that there was another yellow card offence.
"Northampton deserved their victory though so we are not going to take too much out of that for them. My feelings are more frustration that we didn't get our own game on track."
Warriors were without Pat Sanderson for the game with the skipper ruled out with a quad problem.
However, Ruddock insisted his team still should have had enough composure and ability to make us for his loss.
"To lose your number one seven on the week of the game, in particular with the new tackle law directive and new ELVs, was a blow," he said.
"But I was comfortable that the guys we had would be able to negotiate around that and do well.
"We have put a huge amount of focus on to the breakdown it and even brought Hugh Watkins, a former international referee, to oversee our contact and technical sessions to look at this area. To give away so many penalties is a massive concern and something we need to look at."