Arsenal's Mikel Arteta (R) and Santi Cazorla arrive for a training session at their training facility in London Colney, north of London, September 15, 2014. Arsenal are due to play Borussia Dortmund in a Champions League Group D soccer match on Tuesd
“We wanted to give a bit more freedom to Alexis, playing a bit behind Danny [Welbeck], more like a 4-4-2, which we haven't played for a while.” - Mikel Arteta REUTERS/Darren Staples

Arsenal midfielder Mikel Arteta blamed "bad luck" when they lost against Manchester United despite playing their "best game" of the season.

The Gunners were able to keep a clean sheet until 13 minutes after the restart wherein Antonio Valencia's shot got deflected by Kieran Gibbs for an own goal. They had their fair share of chances afterwards, but were ultimately unable to convert.

Red Devils captain Wayne Rooney made it beyond reach at the 85th minute, while Olivier Giroud bagged the consolation in injury time.

"I'm shocked. I think we played our best game this season in terms of what we demand of ourselves - the quality in the way we attacked, how we won the ball back, how consistent we were throughout, the amount of chances we created," said Arteta.

"It's not fair for the players and the fans. How can I explain the result? I can't.

"I am shocked and frustrated because we did not deserve this result considering the opposition we were playing against.

"I can only put it down to bad luck on the first goal which totally changed the game, at a time when we were absolutely controlling and hammering United."

However, the Spaniard did admit that Arsenal's inefficiency in front of goal did cost them the match.

"When you are in the box and you can't manage to score in that many situations, you can't expect to win," he added.

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