Per Mertesacker believes that Arsenal need to address their issues immediately or risk a crisis with the side having blown a 1-0 lead to lose to Swansea on Sunday.
The Gunners had the advantage through Alexis Sanchez after a goalless first half, and while they looked to hold a comfortable lead Swansea broke through their defence in the final 15 minutes, with Gylfi Sigurdsson and Bafetimbi Gomis both scoring to snatch the win.
And on the back of wasting a 3-0 lead over Anderlecht in the Champions League during the week, where the game ended 3-3, Mertesacker admitted that the problems are worse than he thought going into the game against Swansea.
"The game was completely in our hands," he explained, as reported by BBC Sport. "But then we have to play serious football and not make mistakes.
"Anderlecht came back at 3-0 and Swansea came back today from one goal. We have potential, but unless we play that serious football any team will punish us.
"We have to play simple. We think we can do some difficult things, but we need to keep possession. After such a setback as Anderlecht we normally bounce back straight away, but we didn't. We need to work hard on the issues now."
Arsene Wenger also appeared to be at a loss to explain why Arsenal blew a game in which they had looked dominant going into the final 15 minutes, admitting the side's midfield were particularly weak when they were needed to hold the line.
"It is difficult to explain how we lost the lead," he said. "We were in control but they did not give up and we lost some decisive challenges in the middle of the park and we paid for that. That is where we lost the battle.
"We were not in too much trouble, we had the best chances, it is a place that is always tight and it was a very tactical game.
"I worry that we concede the goals, yes. At the moment we have different worries than that [the gap between Arsenal and Chelsea]. We just lost a game that we feel we should not have lost. You have to win the games you can win and today was one. If you want to challenge for the Premier League you have to be a bit more realistic.
"It's disappointing to throw a game away like we did. We were 1-0 up and had to be tight defensively and wait for that second chance. But you have to credit Swansea who didn't give up."