Arsenal goalkeeper Bernd Leno admits Everton knocked them out of their stride for Sunday's 1-0 defeat.
The Germany international made a series of saves, but finished on the losing team.
Leno said, "It's a disappointing result for us. I think we played okay, but we didn't have too many chances to score and we conceded an unlucky goal at the beginning of the game from a throw-in. So it was more difficult to play against a very deep defence and we had problems to create chances.
"I think, like I said, it was very difficult to play against a deep defence. Everton had some chances after transitions, so we have to improve to play against deep defences and to create chances. I think the next games against Watford, for example, will be the same [in terms of facing a deep defence]."
He added: "It's not a good result but we are still in a good position and still in a good atmosphere. It's not a problem to lose one game. We have to keep working hard, work harder and play our style."