Since Mike Johnston's firing and Mike Sullivan's subsequent promotion to head coach of the Penguins, things have looked up VERY much so. The Penguins are fun to watch again, and nearly every player has seen a significant bump in their production, as far as possession metrics go.
Not to mention the differences that the team has seen in their production as well.
This chart does not include the data from the recent game against the Islanders, where there differential dipped a bit, but still, it's easy to see the differences here.
I'm not sure if there is a way to quantify the spike that teams and players get from a coaching change, but I think that this 10-game sample under Mike Sullivan is more than just a spark under the team, but a change of direction in the philosophy of what kind of hockey this team needed to be playing and was built to play.