Arsenal manager Mikel Arteta has admitted that he would love an ‘unbelievable’ ex-teammate to join the Emirates Stadium coaching staff for his knowledge and energy. The Gunners have a close-knit group in the dugout that has helped to guide the team to the quarter-finals of the Champions League and to fight for the Premier League title. But Arteta can see scope to improve Arsenal’s coaching staff, which has rarely changed in recent years. Terry Mason is the only addition that Arteta has made to Arsenal’s backroom team since July 2021. The Gunners promoted him from the academy after two years to…