A couple more points to consider in regards to the cap.
LTIR comes with strings attached.. Leafs only get to recapture cap space on Horton's contract
when it pushes them above the cap ceiling of $71.4 mil. While below max spending his full $5.3 mil is included in Leafs total.
Robidas signed his deal after age +35 and there are also special rules in the CBA for these contracts and the cap consequences. They count against your cap regardless if the player plays or doesn't play even if he retires it still counts. Detroit is in this same pickle with Datsyuk as if he walks away from the NHL and plays in the KHL his full $7.5 mil contract is still on Wings books regardless. Robidas contract is just like this situation unless Leafs capologist Brandon Pridham finds a new loophole (unable to play exemption ?? ) So getting his $3 mil off the books not so easy and last year the full $3 mil counted and Leafs never put him on LTIR knowing it didn't serve any purpose as far as cap relief went. .
Lastly all ELC rookie contracts come with at base amount that counts against the cap and those contracts include various bonuses earned that can increase the base by quite a bit if earned.. There is a 6% overage allowance for those bonuses above the cap ceiling BUT if you can't at end of season fit those ELC Bonuses under the current cap season they get deffered and come of 2017 cap total.
Leafs plan on playing a lot of rookies ie Matthews, Nylander, Marner, Zaitsev and these players are certain to be earning those bonuses which could amount to $4-5 mil essentially depending on which ones are triggered.
The catch 22 here is if the Leafs underspend the Cap ceiling to allow for accommodating Matthews, Marner and Nylanders bonus in 2016 then they can't spend to the cap ceiling to try and nullify Hortons $5.3 mil cap hit on IR.
So pick your poison on that situation essentially cap relief this year (from Horton) verses cap penalties next year as bonus overages carried forwards to 2017 cap.