Arsenal manager Arsene Wenger has discussed a number of different topics after his side’s 1-0 loss to west London club Chelsea.

The league strugglers ran away with victory after a first half strike from Diego Costa gifted them an early lead.

Per Mertesacker’s red card was somewhat of a game-changing, controversial moment, and the Frenchman admitted, as reported by the club’s official website, that it was ‘harsh’ to send the big German off.

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I think it was quick and harsh, but I have to watch it again. What can I change? It doesn’t change anything. The referee made the decision and we have to get on with it. I didn’t speak to Per Mertesacker [about it].

We have 35 journalists here, I am sure you have all seen it again and analysed it and know much more about that situation that I do. I can’t comment because I didn’t know if Costa was offside or not or if Per touched him or not. I don’t know. It was of course frustrating but it is a decision and we had to get on with our job, which we did.

The team [after the red card] was focused and fought until the last second. Despite the disappointing result, we should have even more belief in ourselves after the game, when I see how it went.

Wenger then discussed Olivier Giroud, who, unluckily for him, was substituted for Gabriel Paulista in a tactical change after the 18th minute sending off.

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You want to make a poll for every decision to see who does what? I made the decision and for me it was quite normal. We had to go for long distances and we needed pace to go from one goal to the other. We knew we had to drop deeper and use pace to get forward.

I think yes [he was fit], but it was a bit in my mind if he gets injured, with his ankle, he was a doubt, he didn’t practice yesterday and today we declared him fit. It was on my mind. But I had to change a player and I thought that was the most rational decision with all the factors.

I said Costa got two of our players sent off in the last two games against Chelsea. Those are facts. Was the decision right or wrong, I don’t know but those are facts. Without accusing him of anything.

Theo Walcott was allowed the role of captaincy for the day, in the same week he marked 10 years at the club.

Wenger denied any suggestions the decision to award him the armband was a ‘distraction’.

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Yes [it was planned].

No, you can find many reasons but you never really know. We are frustrated after the game because we could not play with our real assets. I don’t think that is down to Mertesacker giving the captaincy to Walcott.

Alexis Sanchez returned to action for the Gunners against Chelsea and immediately injected some necessary energy into the game, however, his performance was not enough.

Wenger admitted he looked sharp.

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He came on quite well. It took him a while to get into the game but in the last 20 minutes he was sharp.

With Mertesacker being sent off early in the game, the whole tactical approach was changed, meaning Wenger’s side left the game with a number of regrets.

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Today was a special game. We were down to 10 men and we were 1-0 down straight away. Normally you lose a game like that 3-0 or 4-0 when you have to chase it – there is nothing more dangerous when you are down to 10 men. Overall we come out with a lot of regrets because we couldn’t play with our team and looking at Chelsea today there was a lot of room to beat them if we had 11 players.