Chelsea's Costa is again a thorn in Arsenal's side

By Jamie McGeever LONDON (Reuters) - Controversial Chelsea striker Diego Costa proved to be Arsenal's nemesis once again on Sunday, scoring the only goal of a fiery London derby to deny the home side the chance to top the Premier League. The Spaniard also drew the foul from Arsenal defender Per Mertesacker early in the first half which resulted in a red card for the German, a setback from which the Gunners were unable to recover despite the return from injury of their Chilean striker Alexis Sanchez. Costa was a constant thorn in the side of Arsenal's defence, relishing the physical battle on the pitch and appearing to revel in the home fans' abuse directed at him before he went off injured in the second half. He had one clear sight of goal all game, and made it count. Ivanovic whipped in a low cross from the right mid-way through the first half and he lashed the ball into the net from close range. The last time the sides met in September, Costa was also heavily involved as Arsenal lost 2-0 and had two players sent off. A frustrated Wenger told reporters he had not seen the red- card incident again, but noted Costa's role in it. "Costa got two of our players sent off in our last two games against Chelsea," Wenger told reporters. "These are only facts. Was the decision right or wrong? I don't know. But these are the facts, without accusing him of anything. "I think it was quick and harsh but I have to watch it again. Look, we have 25 or 35 journalists here. I'm sure you've all seen it again and know much more about that situation than I do. "I cannot comment on it because at this time I didn't know if Costa was offside or not? Did Mertesacker touch him or not? I don't know." Perhaps unsurprisingly, Chelsea manager Guus Hiddink took a different view. "There was no doubt," the Dutchman told reporters. "You could see it was a beautiful through pass and Diego could run straight through to Petr Cech but was tripped. It's obvious it was a red card, without any discussion." He added: "I'm very pleased with the attitude of the team, but I'm also pleased with the way the team tried to play. It was not just reactive, but proactive." (Reporting by Jamie McGeever. Editing by Rob Hodgetts)