Published: 1 October, 2015 
by STEVE BARNETT

PER Mertesacker admits it has taken the Arsenal players “a couple of days” to get over their disappointing midweek exploits – but says they’re looking forward to getting back on the Emirates pitch this weekend to put things right. 

The Gunners suffered a shock 3-2 home defeat against Olympiacos on Tuesday in the Champions League, a result which leaves them pointless and stranded at the bottom of Group F with tough back-to-back matches against Bayern Munich up next. 

Mertesacker said the performance was “not acceptable”, and is calling on the team to respond in style this Sunday when Manchester United visit north London. “It took a couple of days to recover from Tuesday’s game and to think about Manchester United,” said the Arsenal vice-captain. 

“Sunday will be a good opportunity to come back to the Emirates and play our football with possession and dynamism. 

“We need to get behind the ball and play better defensively. We lacked discipline on Tuesday, even when you get a goal back don’t rush yourself. Get your discipline back and with possession you get your chances.” 

Mertesacker came on as a 57th minute substitute on Tuesday to replace Laurent Koscielny, who limped off with a hamstring injury and is now expected to miss Sunday’s mouthwatering clash against United. 

Arsene Wenger came under fire for benching key players like goalkeeper Petr Cech and Aaron Ramsey against Olympiacos. 

But the Arsenal manager used Koscielny’s injury to explain his actions. 

“It is a hamstring. This is why I rotate as we play many games,” he said. 

“The other teams do it as well. If you look at the benches of the other teams in Europe you will see them rotate. You cannot play every three days without rotating your players. 

“That is a fact and you have to accept that.” 

Arsenal may be forced to play a more open, attacking, game against United on Sunday as Wenger tackles a number of key defensive injuries. Koscielny looks certain to miss out, while Francis Coquelin faces a late fitness test on a swollen knee. Mikel Arteta and Mathieu Flamini are also expected to miss out with their respective thigh and hamstring injuries.