Seeing as to how Draisaitl signed for 8.5M and Evander Kane for 7M, Matthews probably ends up in the 9-10 Million range. Considering Ron Hainsey's contract ending, there would be ~8.5 Million in cap left to sign Marner and Kapanen (Who I think most people expect to make a solid jump this year). If Kane gets 7M, Marner most likely does not get less, so you really have to hope that Kapanen has a **** year for this to work out. Even if that happens, the next year you'll have to worry about resigning Johnsson (Who's getting first line points with matthews) along with Travis Dermott.

Even after all that, I doubt Dallas would retain salary since they need to resign Seguin soon

Matthews - 10.5 +
Marner - 6.5 +
=17 million, which isn't 14 million. Doesn't even include Kapanen, Leivo and Borgman.