The Northern Irishman conceded that his team were "flat" in losing 3-1 at Anfield, while Villains' boss Paul Lambert hailed Christian Benteke's "unbelievable" performance
The hosts dominated the opening periods against Paul Lambert's men but were picked off by some impressive counterattacking as the Villans ran out 3-1 winners.
And Rodgers conceded that his side lacked the intensity they have shown during their recent upturn in form.
He told reporters: "We’re very disappointed. I’ve got to be honest I didn’t see that coming. Our momentum and confidence coming into the game was probably as high as it has been.
"We probably got punished for our decision making in that first 20 minutes and being a bit careless.
"I thought we could very easily have been 3-0 up and if we do that we can control it much better but obviously we didn’t make the final pass or [find] that final bit of quality at that top end of the field and we went on to concede some poor goals.
"We weren’t quite at it today and obviously they were a threat on the counterattack and got the goals.
"[The squad are] very disappointed because that wasn’t us really. That wasn’t how we’ve been. Normally the intensity in our game, we’ve had a good week’s work but I thought we were flat.
"It was going to be important for us today to get the first goal because of the 3-5-2 that Aston Villa were playing, they dropped into a low block and we need that first goal to open up the game.
"But we had those chances early on and didn’t take them and once you couple that with sloppy play and giving the ball away in poor areas, we contrived to concede bad goals."
The Northern Irishman went on to lament referee Neil Swarbrick's failure to award a penalty to Daniel Agger early in the second half, after the Dane had his shirt clearly pulled by Ciaran Clark in the box.
He added: "I thought when it was 2-0, we should have had a penalty, Daniel Agger’s one. I’m not sure what we’re going to have to do to get a penalty.
"You watch that again and, especially now with the referees asked to look at the shirt pulling, he gets pulled to the floor.
"It goes to 2-1 and then you’ve got most of the second half to get that pressure but as soon as the third goal went in we looked that bit deflated and Aston Villa have no need to come out and go after the game.
"They just sit and keep their lines tight and it just looked like a bad day at the office for us."
The 39-year-old did have some positive news for Reds fans, however, revealing that 18-year-old winger Raheem Sterling is close to penning a new deal.
He continued: "That’ll be resolved I’m sure very soon. He’s a good boy. He’s a kid who’s got this special ability to, whatever’s going on, focus on his football and hopefully it stays that way."
Meanwhile, Rodgers' opposite number, Paul Lambert, was understandably delighted with his side's showing, hailing the impact of two-goal hero Christian Benteke and the belief of his young squad.
"I think the whole performance was fabulous," he said.
"The goals were excellent, the way we defended and to come here against a team which is steeped in tradition and history and the way Liverpool have been performing I thought it was a mammoth performance. I thought we were excellent.
"I thought the goals were brilliant, the second goal especially – the movement, the back-heel. Benteke has been unbelievable and Andreas Weimann, what you see is what you get. He’s a natural finisher and his work ethic and enthusiasm for the game of football is second to none.
"I’m pretty sure Liverpool will give anybody a game here with the atmosphere and the players they’ve got, so you expect that it’s just about trying to hold your nerve and trying to see it through and we did that. The back three were terrific for us; young lads put their body on the line when they had to.
"[The squad] will always have the belief that we can win games and you get a lot of satisfaction from seeing them perform the way they do. They’re getting better and better every game and when we’re on song we’re a very good side."