In four of their last five matches Liverpool have conceded from dead-ball situations and Rodgers admits he is concerned by the trend.
The Reds began the season with three straight clean sheets but Rodgers says they must now work hard to cut out the set-piece weaknesses before they become known as a soft touch.
"The more you concede at set-pieces the more you will (gain a reputation)," said Rodgers, who has been tackling the issue with his players after Newcastle became the latest team to score from one last weekend.
"It's just concentration. The ball that came into the box against Newcastle was quite a straightforward one and we just didn't defend it well enough. We went to sleep a little bit.
"I was annoyed at the Crystal Palace one because even though the game was over (it was 3-0 at the time) it was still a goal from a set-piece that you shouldn't concede.
"But it's something that we've worked on and talked about this week in terms of our defensive mentality.
"We started the season with three clean sheets and we just need to get back to that mentality because we know that we can get goals. It is something we need to improve on."
Liverpool have had injuries to the likes of Glen Johnson, Daniel Agger and Jose Enrique and undergone a switch to three central defenders - but Rodgers insists the changes are not to blame for their frailties.
"No, because from a set-piece you are given a job and I think it should be the simplest part of the game in terms of the ball is not moving," he said.
"If you analyse the goals from set-pieces the Southampton goal we just lost our marker and didn't do our job properly on the post.
"The goal we conceded against Manchester United away was from a simple ball into the box from a corner and we lost our man - that was a duel, one v one.
"Again it is individuals. We have coped with set-pieces in the first few games - you just have to ensure every single game your concentration is right or you will concede a goal."