Let's get this out of the way right here: P.O Joseph has done some tremendous things this season in regard to the Penguins' transition game and offensive attack.
Inversely -- although not to the same degree -- he's been giving a hefty chunk of it back to the opposition with his defensive play. It's not the only reason, but that likely played a significant part in him sitting in the press box as a healthy scratch in favor of newly acquired Dmitry Kulikov in each of the Penguins' three games prior to Tuesday night.