Quoting: JaredOfLondon
the same way the sabres move Eichel without retaining. Or even how the leafs moved a guy like zaitsev without retaining. You take shorter over paid contracts, like say, Derek Ryan or Roussel back to make the money work.
Neither Matthews or Marner looked good this series and would argue neither player has shown they are truly elite, especially Marner.
Playoff Stats:
Marner = 32 games played, 25 points and 5 goals (.78ppg)
While Marner's playoff stats aren't bad performances, those stats aren't best in the league and certainly don't warrant the money he's made so far. If he and Matthews can't figure out how to perform when it matters, they are not part of a conversation of "elite".
For comparison, an elite winger
Kane = 136 playoff games, 132 points, 52 goals (.97ppg)
Kane's best playoff performance was only 3 years into his career and he never played next to a Matthews type of player, more often then not with a rotating cast of 17 different centers and besides Panarin, for two seasons which in the playoffs the Hawks ironically never made it far, Kane never had an elite player on the other wing either when he performed his best.
I wouldn't touch Marner's contract for the next 4 years (he's a UFA after that) at that cap hit unless he can show he can step it up in the playoffs and prove he doesn't need Matthews.