The Demons stayed with the Saints for the majority of the game - a few cheap goals in the second quarter aside - before capitulating in the final term, kicking just one goal to four and taking 20 minutes to lodge their first inside 50.
The Saints recorded 17 more attacks inside 50 than the Demons, with the cohesion of latter's forward line a gulf separating the two sides.
Compounding the Demons' loss was a hamstring injury to second-year star Jack Grimes, who will miss at least a fortnight.
Bailey said his side's final-quarter fade was a result of poor decision-making rather than fitness.
"If you're not fluent enough and there isn't enough movement ahead of the ball then the decisions become really hard," Bailey said.
"I just thought we got the ball to halfway, if you like, and then the next part of the jigsaw fell down.
"It's frustrating not to be able to go inside 50, but you have to give St Kilda some credit for the pressure they applied."
Bailey said the Demons' effort was a vast improvement on their woeful performance against the Crows, but consistency still eluded them.
"We improved on last week's game. At least the players responded better for three quarters," he said.
"The score at quarter time suggested it was better. But one quarter or one game isn't enough to do it in. We haven't been good enough for long enough.
"Next week's another challenge to make sure those first quarters are really fought out to the last minutes and the last seconds, because you need to win those first quarters."
Despite the loss, the Demons can look forward to the imminent return of forwards Colin Sylvia and Liam Jurrah, who are both available for selection ahead of this Thursday's game against Essendon at the MCG.
Bailey said the Demons' current position on the ladder - 14th with four wins and a draw - was not a fair reflection on their season.
"At the moment four and half just doesn't sound great," he said.
"It sounds ordinary. We've got another set of games to go and we've got to look at being better than we were today."
