I think we need to move away from "shutdown" lines this year. Move Marner with Matthews making his line better offensively without the defensive vulnerability. Then put Nylander with Tavares and Hyman to give them a more speed and offensive flair. Stop sheltering Matthews and run that line regardless of what the other coach throws on the ice. Nylander will be insane if he plays with puck getters like Hyman and Tavares where he can play the perimeter game.
Matthews and Marner have played with each other for more than 200 minutes at 5v5 over the course of their career. They stink together. There has been no worse linemate for Matthews....ever. And I mean that. Among players who have played more than 200 minutes 5v5 with Matthews, Matthews has been less productive with two players: Hunwick and Polak - but even then he had better underlying numbers with them. CF% with Marner: 47.17%. 46.61 SH%. 41.18% GF% and they did that with 71.88% offensive zone starts. And while Matthews' 2.07 P/60 while with Marner is bad for him. Marner's 1.03 P/60 with Matthews is dreadful for anyone. Matthews and Nylander have produced very well together with very good underlying stats. Marner and Tavares have produced very well together.
Matthews has also never been sheltered. The previous season his QoC was among the very highest in the league. Just because he wasn't used the same way last year doesn't mean he was sheltered.