Arsene Wenger says Diego Costa got Per Mertesacker sent off as Arsenal lose to Chelsea AGAIN

Arsene Wenger says Diego Costa got Per Mertesacker sent off as Arsenal slumped toyet another defeat against Chelsea .

The Gunners' misery started just 20 minutes into the match when Mertesacker slid in and brought down Costa , who was through on goal.

Wenger was unhappy with the decision to send off the defender, despite Mertesacker and the supporters appearing to have few arguments with Mark Clattenburg's call.

"I can't influence the decision of the referee. I thought it was harsh and we had to cope with it," he said.

"I don't know what to say. It is a few games now that has happened. All we can do is keep our focus and fight."

Mertesacker dived in and took down Costa...

...which sent Costa tumbling to the ground...l

...before receiving his marching orders

When asked if he thought Costa made the most of the situation, he said: "Yes . That is the game of the striker. Diego Costa is good at that."

He continued: "The referee was very quick to take the red card out. We coped with the decision well and should have had a draw at least. We had the chances to get a draw.

"Mentally we were focused. Sometimes when you lose you can still say 'well done' to the players."

Wenger was booed for his decision to replace top goalscorer Olivier Giroud as he reshaped the team following the red card.

Olivier Giroud was not happy about being subbed off.

...and expressed his disappointment on the bench

Gabriel Paulista entered the pitch but there was a chorus of boos and jeers around the Emirates.

Wenger said: "The fact is we needed to get strength on the counter-attack and needed pace. That is why I made the decision.

"It is not a coincidence that after 23 games Leicester are still there. But there is a long way to go. What we take from today is that we are disappointed but have a lot of positives from our attitude and spirit."