A subdued and sombre Arsene Wenger was left to rue Arsenal’s lack of efficiency after his team lost 2-1 at home to Manchester United on Saturday in a game they dominated. ‘We have not dominated many games against United like we did today but we were not efficient enough and made defensive mistakes. We had plenty of opportunities to win the game and we are very disappointed. We were a bit naive,’ Wenger told a news conference. Wenger’s misery was compounded by injuries to midfielder Jack Wilshere and goalkeeper Wojciech Szczesny, who were both forced off in the second half. ‘Jack has an ankle injury. I don’t know how bad it is yet. Wojciech is not bad,’ he said.Arsenal have slipped to eighth in the EPL table, 15 points behind Jose Mourinho’s Chelsea.