The Gunners have won all their matches so far in Group B but are finding it hard to replicate similar form domestically.
Arteta’s men have won only one game out of their last five Premier League games and currently sit 14th on the Premier League table with just 13 points.
"The aggressiveness is always there but the margins in the Premier League are so much smaller, when you make a mistake you pay the price,” the Spanish coach said after the game.
“We haven't been as ruthless in the final third in the Premier League as we have in Europe, but I liked the reaction of the team and the performance.
"Many of them I am delighted with, the injured players who been out for so long they worked so hard we are so glad to have them back, to add numbers to the squad.”
“[Alexandre] Lacazaette it was great to have him on the score sheet, some really good individual performances and some of the good from the young boys as well.
"The club has made such an effort to make sure today everything was set up in the right way so hopefully the fans had a good night, they were tremendous for us."
Next up for Arsenal is a short trip across town to meet local rivals Tottenham Hotspur in the Premier League on Sunday.
