Why has Sean Couturier been demoted to 4C, and how can he get his old role back?

Surprised that Sean Couturier was centering the fourth line on Tuesday and appears poised to stay there entering a pivotal weekend for the club?
John Tortorella doesn't think you should be.
"(Scott Laughton) was a fourth line center. (Earlier in the year) you guys were shocked he was a fourth line (center)," Tortorella pointed out. "I don’t do by – and it’s certainly not a disrespect in any fashion to the player -- I’m not gonna run the bench based on what people think about you, or where you sit as a veteran guy, a captain. I just don’t do it that way.”
Even if it's the highest paid player on the team, who was receiving 20+ minutes a night as recently as as a month ago, and just had the "C"...