"Arsenal" defender Mikel Arteta warned his teammates that they need to step up in the future if they want to achieve impressive victories in the UEFA Champions League.
The London club lost their first away game 0-2 against Dortmund's "Borussia".
"If we continue to make such mistakes against the strongest teams, then we have no chance of triumphing in the Champions League," said the Spaniard.
"We encouraged the opponents to attack, as we often lost the ball in various situations. The Germans took advantage of the opportunities created and put additional pressure on us.
I am very disappointed because we knew the strong points of "Borussia" and what we should avoid, but still allowed them to shine," Arteta concluded.
