As others have stated, he certainly needs some work in the defensive end.
Not to mention how much space he's been getting on the ice compared to Gardiner, with other teams trying to cover the talent that OKC has on the ice at all times.
I think Schultz is going to be a very good NHL'er someday, and he'll put up great offensive stats from the blueline, but he'll always leave much to be desired on the defensive end.
Gardiner on the other hand is a bit better two-ways and has the raw talent to be able to hone his offensive skills to the point where he could quarterback an NHL Power Play.
Schultz will always have the better ability to make more of an impact on any give game either for good or for bad, but Gardiner IMO will always be the safer bet with consistent numbers on both ends.
Kostka on the other hand will probably follow the career path of Keith Aucoin. He's deserving of a shot at an NHL call-up, but I dont think he'll be the Leafs first option when we get back to playing. Paul Ranger is steadily improving and getting himself into his former shape. He's feeling more and more comfortable, confident and energetic every shift.
Cant wait to see what Ranger can do with a year of steady hockey under his belt.