Unai Emery insists Arsenal must improve their defensive displays after shipping late goals to Europa League minnows Vorskla Poltava.
The Gunners raced into a four-goal lead as a Pierre-Emerick Aubameyang double, a Danny Welbeck header and a tap-in from substitute Mesut Ozil set them up for a big win.
But Vorskla rallied and halved the arrears as Volodymyr Chesnakov pulled one back before Vyacheslav Sharpar scored with the final kick of the evening as the opening Group E clash ended 4-2.
Head coach Emery made eight changes from the weekend win at Newcastle as goalkeeper Bernd Leno was handed his debut.
But, in conceding to the Ukrainian Premier League outfit, Emery has yet to see his Arsenal side keep a clean sheet and he knows it is an area where the team need to sharpen up.
“It’s our disappointment today,” he said of the two goals.
“Little by little, we are conceding a few chances to the opposition, the same like in Newcastle.
“But we need to continue to improve on this because in the last minute in Newcastle and again today in the last 20 minutes, we conceded two goals.
“Our challenge is to be competitive for 90 minutes of each match and this is one thing to improve.”
The late strikes also means that Arsenal are yet to keep a clean sheet in any of Emery’s first five games.
“We are speaking before each match to take a mentality of ‘don’t concede chances easily’,” he added.
“I think today is a good opportunity for not accepting goals, but the last 30 minutes, we needed to be better on this competitive aspect.”
“We lost against a good team today, but it’s good experience for us,” he said.
“A few of the lads need to believe in themselves. Fate is what it is, and today’s match shows us what we’re aiming for.
“We stuck to our game plan for a long time, we were able to help each other out, the lads gave everything on the pitch.
“They knew that we couldn’t open ourselves up, because Arsenal’s attack is so quick.”