Arsenal boss Arsene Wenger says his side should have done better defensively in Tuesday's 3-0 away defeat at Sheffield Wednesday.
The Owls reached the quarter-finals of the League Cup after producing an impressive performance at the Hillsborough Stadium.
And the Frenchman says the double injury suffered by Theo Walcott and Alex Oxlade-Chamberlain is a big blow ahead upcoming games against Swansea City and Bayern Munich.
"It was a very bad night for us," Wenger is quoted as saying by the BBC.
"We lost two important players in the first part of the game and then we were not at the level we needed to be.
"Congratulations to them, they were faster, sharper and more decisive than us. We could not create anything. We were very naive when defending.
"We cannot master how people will react. I left six players at home and I still lost two to injury.
"The level was too high for the young players tonight. They are not ready to play at this level.
"We are short now with the injuries. It is a big blow for us."