I'd add to this the need for a legitimate, in his prime, top pairing right handed defenseman to play with Rielly, so the pair can play 25 minutes per night when need be. That would cement an excellent top 4, IMO, of...
Rielly / Addition
McCabe / Liljegren
Imagine for a second if you added a right handed version of Zack Werenski, at 26 years old, just coming into his prime, signed for 4 more years beyond this one, at $9.5 million per year. Send Marner the other way in the deal, free up some cap space, while re-balancing your roster and running 29 year old Morgan Rielly and that guy together for the next 5 years. Meanwhile Jake McCabe and Timothy Liljegren could play together every night to round out your top 4.