Mikel Arteta said Arsenal are "conceding too many simple goals" after his side's 2-2 draw with Sporting Lisbon in the Europa League.The Gunners went 1-0 up in Portugal before their hosts turned the game on its head to lead 2-1, with a Hidemasa Morita own goal ensuring the tie is all square heading back to the Emirates. "We are conceding too many simple goals, and we talked about the importance of boxes, and especially in competition when you are in and out," Arteta said after the draw. "Today, we didn't defend that well enough."