The Saints were in the game until half time before the Crows opened the floodgates in the second half kicking eight goals to three.
"Our efficiency when we had opportunities early in the game wasn't where it needed to be," Watters said.
"I don’t think we were able to really deliver the effort that was required over 4 quarters to stay in the game.
"It didn't feel like we were flash tonight or super sharp, but it was a pretty big drop off in the second half, so we've got to freshen up and learn from that and butter up for next week."
St Kilda lost all the key indicators in the match. They had 7 fewer contested possessions, laid 5 fewer tackles, allowed 8 more inside 50's and lost the clearances by 5.
"Centre bounces were an issue for us. I thought they got great momentum and field position of the back of that," Watters remarked.
"We were unable to limit their uncontested ball, [they had] a lot of uncontested marks."
Leigh Montagna was St Kilda's best with 34 possessions.
Nick Riewoldt worked hard around the ground and Sean Dempster played well on Patrick Dangerfield, but it wasn't enough to stop the Crows running away with the game in the second half.
Watters felt their fadeout had nothing to do with their 6-day-break following Monday night's win over Carlton.
"If I make an excuse for that now I'm going to have to make an excuse for that in another 6 days so we're not into that," he said.
"Jarryn Geary continues to get some big roles and play well, I thought Sean Demptser was pretty solid tonight (and) Nick Riewoldt's work rate I don't think can be questioned.
"So there are still a lot of positives and for half a game of footy, with I guess a few young players out there, they hung pretty tough, but obviously there's some improvements for us and some learning from the second half."
St Kilda hopes to bounce-back against the Western Bulldogs at Etihad Stadium on Saturday.
