Tottenham, however, were dumped out of the competition after losing 3-0 in Dinamo Zagreb – and Arteta says that is warning for everyone.
“It shows as well the level of the opposition,” he said.
“People take for granted that you play against any opponent and you’re going to be through because of the name of the club they represent. It’s not like that. Every team in Europe is really difficult to beat.”
Asked if his side can’t afford to perform as poorly as they did against Olympiacos, Arteta said: “Yes.
“Because what we have to do, the way we are setup, the organisation we have and the way we want to play, we have to be much more efficient, much more simple, much more cohesive as a team.
“Without that structure you are exposed when you lose the ball in really dangerous areas without any opposition.
“When you do that, and we did that as well where we created chance after chance, but again, as you mentioned we want to be in the competition, and when you have four, five, six big chances in Europe you have to put them away and then the tie is over.”