Sunderland manager Steve Bruce admits his side's wastefulness in front of goal remains a concern, following Tuesday's Carling Cup loss at Brighton.
The Black Cats have scored just once this season and missed chances in the 1-0 defeat at the Amex Stadium.
"The difference between a Premier League and a Championship team should be the ability to take chances, it's a big concern," Bruce told BBC Newcastle.
"It's not acceptable to keep creating glorious chances and not taking them."
Bruce added: "We've created enough chances, with the quality that we have got, but at the moment it's our Achilles heel, and we've been punished."
Sebastian Larsson's equaliser against Liverpool on the opening day remains Sunderland's only strike this season, with last weekend's derby at home to Newcastle United ending in 1-0 defeat.
Tuesday's defeat ended Sunderland's interest in the Carling Cup at the second round stage, extending a disappointing run which has seen the club go no further than the fourth round since 2000-01.
"We've come to take it seriously because we knew what it meant," Bruce added.
"Unfortunately we haven't been good enough on the night to take our chances and win us the match.
The Black Cats return to Premier League action on Saturday with a visit to newly-promoted Swansea City.