The Boston Celtics will look a whole lot different this fall. The Celtics already had enjoyed a big summer before they struck a massive blockbuster trade Tuesday, acquiring All-Star point guard Kyrie Irving from the Cleveland Cavaliers in exchange for Isaiah Thomas, Jae Crowder, Ante Zizic and the Brooklyn Nets’ 2018 first-round draft pick. Irving coming to Boston means he’ll have to pick a new jersey number, as the No. 2 he wore in Cleveland is retired by the Celtics in honor of legendary coach and team president Red Auerbach. And judging by the Celtics’ Instagram account, Irving already has made his choice.