Arsene Wenger admits his side are going through a difficult moment after their 2-1 defeat to West Brom at the weekend. The Gunners slipped to a surprise loss against Tony Pulis' men after Santi Cazorla missed a penalty late on. The boss claimed the defeat was a nightmare, as they look ahead to the game with Dynamo Zagreb in Arsenal's must-win Champions League clash. In other news, Mathieu Flamini has refused to blame the Spaniard for the penalty miss that condemned the north London side to their first league defeat since mid-September. The Frenchman said his side have no excuses for the defeat and there was nothing Cazorla could have done about falling when taking the spot kick.