Per Mertesacker: Arsenal dropped mentally after the Manchester United game, but we came back in an even stronger way

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Per Mertesacker admits Arsenal dropped mentally after losing to Manchester United on Saturday, but says they came back even stronger to beat Borussia Dortmund in the Champions League.

The Arsenal defender partnered Nacho Monreal at centre-back for both games, and hailed the solidity of the defence in the wake of Wednesday's Champions League win.

When asked what the key was to the victory, Mertesacker told Sky Sports: 'The solid performance, especially defensively. We didn't give them too much, especially in the second half. We were solid at the back.

Per Mertesacker (centre) congratulates Yaya Sanogo after he scored to put Arsenal 1-0 up against Dortmund

Mertesacker praised Arsenal's defensive spirit after the game, and says they came out stronger than before

'Today was a mental task, but we are strong enough so we continue now.

'It was good (to get the early goal) but you have to play another 89 minutes. Over 90, we played absolutely solid.

'After Anderlecht and Manchester United, we dropped mentally a bit, but today we came back in an even stronger way. We learned from disappointment in other weeks.'

Arsenal's win over Dortmund secured their place in the last 16 of the Champions League, enabling their focus to turn fully to the Premier League season.

Mertesacker (right) high-fives Arsenal goalkeeper Emiliano Martinez after Arsenal kept a clean sheet

Mertesacker was happy on Wednesday, but not so much on Saturday (pictured) when they lost to Man United

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The Gunners are lagging in eighth position, and face a trip to West Brom on Saturday.

'We would like to (be consistent). Saturday, an early kick off away, we have to prove ourselves. That was a fantastic start, and we're through to the knockout stages.

'Lets concentrate on the league, we have some big weeks coming up.'