For me, it looks like the original Matthews injury forced the team to move quickly into Berube style hockey, and they thrived, taking many steps towards becoming a different team looking to tune up for a playoff run.
Marner found a nice rhythm, elevated his game to new heights, Tavares looks rejuvenated engaged, driving, Nylander has kept rolling, etc, the defense and goaltending was great for the entire month of November. Everything just looked so north south, clean, simple, etc.
Then Matthews comes back. For the most part he's been okay, but the off nights and Marner pairing kind of shows me he's either not healthy, or lost in the transition to Berube hockey.
Compared to everyone else his skating routes look lazy. Sometimes it looks like he doesn't want to get there. He gets to a puck battle and isn't fighting for anything. On a line with Marner and Knies/Pacioretty, he's the most passive one. Not generating offense. Not carrying the puck. Falling into old comfortable patterns.
It looks like the team took steps towards playing harder and Matthews has either been left behind or he's decided he wants to play Steven Stamkos hockey, which is a faux center, 5 on 5 ghost who looks for the switch flipping goal.