Arsene Wenger was left to rue the impact of Diego Costa as 10-man Arsenal were undone by Chelsea yet again.
Costa in September tussled with Laurent Koscielny and Gabriel, who was sent off, and drew a foul from Per Mertesacker which saw the German dismissed at the Emirates Stadium in Chelsea’s 1-0 win.
The Chelsea striker then netted his sixth goal in six games to dent the Gunners’ title hopes and extend their winless league run against their derby rivals to nine games.
“He got Mertesacker sent off,” Wenger told Sky Sports 1 after Sunday’s match.
“I haven’t seen it again, I said in the first game he got Gabriel sent off and today he got Mertesacker sent off. He is clever. A fact is a fact, I do not accuse him of anything, it’s just what happened.”
Asked about the incident later in his post-match press conference, Wenger said: “I said Costa got two of our players sent off in the last two games against Chelsea. Those are only facts.
“Is the decision right or wrong? I don’t know. That is a fact, without accusing him of anything.”
Wenger had not seen the incident again nor spoken to Mertesacker, but described referee Mark Clattenburg’s decision in the 18th minute as “quick and harsh”.
Chelsea interim boss Guus Hiddink said it was “obvious” and pointed to the decision to deny Cesc Fabregas a penalty when Koscielny body-checked the playmaker.
“There was no doubt. From what I saw he was tripped,” said Hiddink, who said Costa was substituted in part due to a knee problem.
“I had some doubts over the Fabregas penalty, yes or no. I can understand why the referee didn’t give a penalty, fair enough.
“But on Mertesacker’s red card, look closely. It was obvious I think.”
Wenger declined to address Costa’s role further, but was frustrated not to make the most of the opportunity against a Chelsea side whose title defence has fallen apart this season.
He added: “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 played with 11 players.”
Wenger praised his team, despite a fifth loss of the season which leaves them three points behind Leicester in third place.
“Despite the disappointing result, we should have even more belief in ourselves after the game,” Wenger said.
“The team were focused and resilient, fighting to the last second.”
Hiddink is now unbeaten in seven matches and the Blues undefeated in eight since Jose Mourinho’s departure last month.
Captain John Terry believes a top-four place and Champions League qualification is not beyond them, but fourth-placed Tottenham are 14 points ahead with 15 games to go.
Hiddink said: “With that gap, it’s difficult to go into fourth position. But when the captain is saying that, I will follow my captain.”