In his sixth year with the Bruins in the 2015–16 season, and in the final year of his contract, Kelly began the campaign leading the Bruins penalty-kill. Kelly scored 2 goals in 11 games before on November 3, 2015, he buckled his left leg on the ice and broke his left femur in a game against the Dallas Stars. He was announced to have undergone surgery the following day and was scheduled to have a 6-8 month recovery period, which effectively ruled him out for the season.