Tatar is likely expecting a raise. Mantha gives you cost certainty.
Moving out Tatar and Danault, and moving in Mantha , Caufield, using Evans/Poehling and maybe a cheap 4th line faceoff specialist allows you to maintain your depth.
Exactly the way I see it playing out
Lek is resigned and Armia is a maybe as well
Mantha has flaws but is playing for a crappy team , I think he does well in Montreal going back home
I think Nero doesnt want to go term with too many more vets