The Northern Irishman conceded that his team was "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 it has shown during its 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.
"[The squad is] 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.
"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.
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."