Aston Villa defender Carlos Cuellar insists the team are frustrated by mistakes, especially their defenders.
Individual errors accounted for two of Villa's goals in last weekend's 3-0 defeat by in-form Arsenal at Emirates Stadium.
The Spanish stopper has held his hand up after losing possession in the build-up to Arsenal's second from Theo Walcott.
Villa have won just one of their last seven Premier League outings and Cuellar insists it is not a confidence issue, just concentration.
"It was very frustrating for the whole team and for the defenders in particular," he told the Express and Star.
"If you look at two of the goals against Arsenal they were both individual mistakes.
"For Mikel Arteta's amazing free-kick you can do nothing, but for the other two we were not good enough with our concentration.
"I made a mistake with one ball which led to a goal and know that is not good enough.
"We have not lost confidence though and at home it will be much better for us."
Cuellar was happy enough with Villa's form prior to losing to the Gunners, although he knows the visit of Chelsea this weekend will pose a stern test.
He continued: "I think we were doing well until this game. We knew it would be a really hard game for us because Arsenal are such a good side with the players they have got.
"We also have good players and we were doing so well but we must try to keep our confidence ahead of the game at Villa Park against Chelsea, which will be a big one for us."