The Blues controlled the game for the first 60 minutes and took the lead when Joao Pedro capitalised on Reece James’ corner in the 39th minute.
Despite further chances through Cole Palmer and James, Chelsea failed to extend their advantage, allowing manager Unai Emery to make three impactful substitutions.
Those changes proved decisive as Ollie Watkins came off the bench to score a second-half double, turning the match on its head.
Ahead of their next home fixture against Bournemouth, Maresca admitted he remains at a loss to explain his team’s inability to maintain control and hold onto leads this term.
“It's just a matter to understand the reason why,” he told media
“When something continues to happen, it's not random. We need to understand why. No matter if we're winning, drawing or losing, when we concede a goal we lose a little bit of control.
“For one hour we can take many positive things,” he continued.
“Not many teams create so many chances against (Villa). First half they were zero in terms of xG (expected goals), they didn't create anything.
“I watched the Arsenal game (when Villa won 2-1 at Villa Park) and the games they have won, and they always create. The game doesn't reflect the 10 points difference between us and Aston Villa to be honest.”