Chris Boyd' s side bagged a bonus-point win at Sixways, keeping them in touch with the Gallagher Premiership play-off places.
Saints were 19-3 up at half-time thanks to tries from Rory Hutchinson, Sam Matavesi and Alex Mitchell.
And though Worcester fought back after the break, scoring two quick tries, Saints finished the job as James Fish secured the crucial fourth try.
“I thought we were competitive, but the scoreline doesn’t suggest that,” said Diamond, who is currently Worcester's lead rugby consultant but will step up to become director of rugby this summer.
“Our defensive frailties were evident in the first half, but it is a work in progress and we will be putting some graft into those areas.
“Half-time was reasonably calm, and I thought we were in the game in the second half. We missed a couple of opportunities.
“We must have given four of the penalties that we gave away in the attacking 22, which is unacceptable at this level.
“We have got great players and we have got a good coaching team, and it just needs a little direction and little bit more tuning in on the basics, and I think we will be okay.
“We couldn’t get the result that certainly I was looking for, but there are a lot of positives to take out of it.”