Christian Benteke scored twice on either side of an Andreas Weimann strike before Steven Gerrard collected a late consolation.
The Liverpool manager felt all three goals against were avoidable but remained confident that the result was merely a stumble on his side’s march up the Barclays Premier League table.
“It was a bad day at the office,” Rodgers told reporters after Liverpool’s three-game winning streak ended.
“We’re very disappointed and, I’ve got to be honest, I didn’t see that coming. Our momentum and confidence coming into the game was as high as it’s been. We had chances early on and didn’t take them.
“We could easily have been 3-0 up in the game, but we didn’t make the final pass or have that bit of quality in the top end of the field, and then we went on to concede some poor goals.
“The first goal we gave the ball away in our half of the field, and then our positioning wasn’t great — Benteke gets the shot in too easily. The second goal we never tracked the runners into the box and the third, again, we gave the ball away in our own half.
“We’re normally much stronger than that defensively, so there is no doubt that, without taking too much from Aston Villa, it was very much self-inflicted today.
“It was always going to be important for us to score first today because with 3-5-2, Aston Villa could drop into a low block and make it difficult.
“The lads are very disappointed, because that wasn’t us. That wasn’t how we’ve been. We’ve had a good week’s work, but we were flat.”
Liverpool now faces Fulham at home next weekend before Christmas trips to Stoke and QPR.
“All week we’ve been talking about the possibility of top four, but for us it’s going to be steady progress,” Rodgers said. “There are going to be steps forwards, like we’ve done in the last couple of weeks, and today we made a step backwards.
“The great hope with this group is that they are very honest. They’re bitterly disappointed. We all are. But we’ll go into next week’s work, reflect on it, and make sure we come back next week and are bang on where we’ve been for a lot of the season, which has been a much greater intensity to our game.”
Anfield protested for several penalties during the 90 minutes, and Rodgers felt referee Neil Swarbrick was wrong to deny Daniel Agger a foul after he was held inside the box.
“I thought when it was 2-0 we should have had a penalty, Agger’s one,” he said. “I’m not sure what we’re going to have to do to get a penalty.
“I thought Agger was outstanding today, and he got pulled to the floor. That could have made it 2-1, and you’ve got the rest of the second half to get that pressure.”
Meanwhile, Rodgers explained that his decision to replace Jonjo Shelvey with Joe Cole at halftime was tactical rather than due to injury.
“Jonjo is fine,” he said. “We were down in the game, and we wanted to get the wingers inside more, and Joe had come on in the last game and scored a goal. That was purely tactical to try and change the flow of the game.”