According to Marc D'Amico of Celtics.com, Isaiah Thomas, who is really well-liked around the NBA, was approached by another player at the all-star game and asked about what it was like to play for the Celtics. The implication being that this unidentified player was interested in coming to Boston:
#IsaiahThomas says a player, who he will not name, asked him about Boston... As in that player is interested in joining the Celtics.
Who could this be? Well, here is a list of every NBA all-star either involved in trade rumors or approaching free agency this summer:
Al Horford
DeMar DeRozan
Given DeRozan's reported interest in joining the Los Angeles Lakers this summer, which makes sense considering he is from California and played college ball at USC, my guess is the unidentified player who approached Isaiah Thomas was Al Horford, who we now know wants to join the Celtics and that may gain him some admirers in Boston.