I watched the series. I'm a hockey fan in general, but man I was raging at Gardiner, I get emotional.
Now that I've calmed down, I think that in order to keep Gardiner, you have to partner him with a defense-first partner, one that is able to cover for him. So at the end of the day Leafs need an improvement in D (everyone knows this).
But it's a salary cap world. Ideally JD would get PP-time and more O-zone starts, although he is good at moving the puck out of the D-zone.
I guess this is just stating the obvious. In an ideal world partner him with a D-first, mobile and responsible partner.