We'd need to protect him in expansion and so one of our D is gone from our top 4. Is it Holl, Muzzin, Rielly, or Brodie? And who does he upgrade us on? I think upgrading our second pair if it's Holl for the cost doesn't make sense given how well Holl has played. On top of that, it basically means Dermott is gone as well as the Leafs would have 10 NHL dmen (Rielly, Brodie, Muzzin, Holl, Ekholm, Dermott, Bogosian, Sandin, Lehtonen, then Liljegren/Rosen/Marincin).
I think an upgrade to our secondary scoring is a much bigger need. Defensive numbers look good this year, it' our goaltending killing us most nights if you believe advanced stats.