England centre Mark Percival scored a hat-trick and Australian full-back Ben Barba produced a man-of-the-match display as Saints ran in eight tries to one to reduce the 2017 league leaders to a rabble.
"Saints played very well and put us under a fair bit of pressure but I thought we were pretty embarrassing to be honest," Powell told Sky Sports.
"We consistently lost the ruck area and Saints ended up pulling us apart on the back of that.
