Clever Costa created Mertesacker's sending off, says Wenger
Arsène Wenger admitted Arsenal fell foul of Diego Costa once again after the Chelsea forward scored the only goal of the game to seal victory at the Emirates after sparking the first-half dismissal of Per Mertesacker.
Costa, who was at the centre of red cards for Gabriel and Santi Cazorla during Chelsea's 2-0 victory against Arsenal at Stamford Bridge last September, saw Mertesacker dismissed by referee Mark Clattenburg in the 18th minute after the German's clumsy challenge felled the striker.
But while Wenger refused to condemn the former Atletico Madrid forward, the Arsenal manager made clear his frustration with the player's propensity to earn red cards for his players.
"Costa got two of our players sent off in our last game against Chelsea, but these are facts," Wenger said. "This is not accusing him of anything, it is just facts. So he's clever. Mertesacker made the challenge but he got Mertesacker sent off. You cannot say it's not true. The referee was very quick to take the red card out. I can't influence the decision of the referee, but I thought it was harsh and we had to cope with it. I don't know what to say. It is a few games now that has happened. That is the game of the striker.
"I cannot comment on whether Costa was offside or if Mertsekacker touched him, but you have to take it on the chin and get on with it."
With Mertesacker clearly the last defender, Clattenburg had little option but to dismiss the German international and the Chelsea interim manager, Guus Hiddink, admitted his surprise that the decision was even in question.
"There was no doubt because you could see it was a beautiful through pass and Diego could run straight to Cech, but he was tripped," Hiddink said. "It was obvious then that it was a red card without any discussion."
Arsenal's defeat extends their poor run against Chelsea to one win in nine league encounters and also denied Wenger's team the chance to dislodge Leicester City at the top of the table.
But the Frenchman insists that there are positives to take from his team's defeat.
"We should have had a draw at least," Wenger said. "We had the chances to get a draw and mentally we were focused.
"Sometimes when you lose you can still say 'well done' to the players, so we come out of this game with more belief in ourselves."
Chelsea are now seven games unbeaten in the league under Hiddink, who took over last month. But while the champions lie in 13th position, 14 points adrift of the top four, the Dutchman admits a late surge into the Champions League qualification positions is not impossible.
"It's a gap and if you see the results and how competitive it is, it is unpredictable and all teams can beat everybody else, so it is difficult to make the top four," Hiddink said. "But if the captain, John Terry, says we can do it, then we follow the captain!"