The Boston Celtics, as evidenced by their start to Game 1 of the Eastern Conference finals, probably still are a few players away from competing with the NBA’s elite — the Cleveland Cavaliers and Golden State Warriors. But they are in a position to put a dent in that deficit this offseason. The C’s have the No. 1 overall pick in the 2017 NBA Draft, and they also could sign another top free agent, similar to their approach last offseason when they drafted Jaylen Brown and signed Al Horford. But who would that free agent be? The Vertical’s Chris Mannix has a pretty good idea. “The next step for this team, that’s got to be Gordon Hayward,” Mannix said on CSNNE’s “Celtics Pregame Live.” “That is a guy who can help this team immediately. And that’s a guy I believe is Boston’s No. 1 target this summer.”