There is a domino effect you need someone to step in for Guhle and you have to someone else stepping up for that guy and so on... It isn't just the minutes, now your playing 22min vs. 17min but your also playing vs. higher competion.. Matheson is playing over 25min, if the guys we had couldn't take a 3-4 extra minutes this years, next year they will take all 25min...
Even if you take out the PP Matheson is still a legit Top4 D, the contrat is out of this world look at all the D make more than him over the next 2 years this won't be a anchor at any point and he want to play here. Matheson is expendable just like Turgeon was expandable and even if he is the odd man out (which he could still be), you can't just give him away, if you aren't getting significant return your better off just keeping him.