Wenger knows such costly lapses in concentration at the back must be eradicated if his side are to keep within striking distance of the top four.
"We were defensively fragile, were not cautious enough at 2-0 and we let them back into the game because we lacked urgency," the Arsenal manager said.
"We showed magnificent spirit in the second half, but the team has to learn to deal better with this kind of situation.
"There are good ingredients in this team, a good spirit, but we need a bit more defensively when we are leading the game."
Wenger added: "At the moment, we do not get the points we want. Of course, we now do not have to waste any more time, but I still feel there is good potential in our side."