Bernd Leno admits we won't win the Europa League if we don't improve on our second-leg display against Olympiacos.
We advanced to the last eight of the competition on Thursday but a 1-0 defeat made our 3-2 aggregate win more uncomfortable than it should have been.
"I think we suffered today and it was not necessary," Leno told Arsenal Media.
"I think because in the first 15 or 20 minutes we controlled the game but then we've made too many easy mistakes and in the second half we conceded the goal and then everybody was nervous.
"We made it hard for ourselves and, like I said, it was not necessary.
"In the dressing room it was quiet because everybody knows that it was not a good performance from us. We cannot change it anymore but the positive thing is that it was a warning.
"We need to be 100 per cent every game. If we play like today then we won't reach anything this season.
"I think there are only very good teams in the quarter-finals and we need two perfect games to go to the semi-finals and two more games to go to the final.
"The Europa League is very important for us," added Leno. "This is probably the closest way to go to the Champions League and also to win a big European trophy so we need to step up.
"We need to have the motivation to win every game, cut out the easy mistakes and go through to the final and hopefully have a big final at the end of the season."
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