Defender Per Mertesacker feels Arsenal must show more discipline if they are to stand any chance of progression in the Champions League.

The Gunners slipped to their second consecutive defeat in this season’s elite club competition on Tuesday with a 3-2 home defeat to Greek side Olympiacos.

It leaves the north London outfit hanging on to qualification for the knock-out stage by the skin of their teeth and it is now likely they will need to win at least three of their remaining four games to stand any chance of being in the competition after Christmas.

Arsene Wenger’s side were 2-1 down at the break but rallied to level affairs as Alexis Sanchez netted on 65 minutes.

But 60 seconds later the hosts were behind again when Alfred Finnbogason found the back of the net.

Back-to-back games with in-form German giants Bayern Munich now follow and it looks set to be a tough few weeks for the Emirates outfit.

And Mertesacker pulled no punches in his assessment of what is going wrong with Arsenal at present.

“We need to get behind the ball and play better defensively,” he said. “We lacked discipline, even when you get a goal back don’t rush yourself.

“Get your discipline back and with possession you get your chances. If we are not disciplined and do not chase the ball we have got no chance.”

Things will not get any easier in the Premier League as table-topping Manchester United are the visitors on Sunday and can be backed at 3.60 to leave the capital with all three points while the home side are on offer at 2.00.