Last year's was probably unsustainable because we were playing possession based attacking football with exactly one player in the side suited to that.
This year we're playing extremely direct and the natural athleticism that many in the team have to make it work. Adding Diaz would only enhance this. So it might, might stick.
We do have areas to improve because for example we won't be getting a penalty every week, but there is reason to think we could still be better from open play. We've got in a lot of decent positions and made bad decisions. That's something we can sort.