The plan is, evidently, to keep William Nylander in the NHL. Mike Babcock already flat out said as much the morning of his ninth NHL game:
Mike Babcock says there's no question he would keep William Nylander for the rest of the season.— Chris Johnston (@reporterchris) March 15, 2016
And it appears the Maple Leafs are officially putting their money where their mouths are. Or where Nylander's is, because this is going to bring him one year closer to a new contract.
Babcock says Nylander will play his 10th game tomorrow and burn the first year of his contract.— James Mirtle (@mirtle) March 16, 2016
And there you have it. With just 13 NHL games to go, Nylander is presumably playing in all of them (barring any sort of unforeseen event). That'll give him 22 NHL games total for the first year of his entry-level contract: meaning come the 2018-19 season, Nylander is going to need a new deal.
If he turns out as the Leafs hope, that means Nylander is going to get paid one year earlier than he otherwise might have been.
Now, it's not as though the Leafs are exactly hurting for cap space, but things can change pretty quickly over the course of a few years. At the same time, sitting down one of the major futures of your franchise and telling him, "Yeah, you have to go back a level because we want to save money on you," probably isn't going to go well. Once he was brought up and performed like, well, William Nylander, he was probably up to stay.
This doesn't mean his AHL days are fully behind him, though. The Leafs' season will end before the Marlies', and what with Toronto having the best AHL team, he can likely be expected back to help out in the playoffs. He's going to have to get that experience somewhere, after all!
But for now? Sit back, enjoy some extra Nylander games on TV, and try not to think about how much he'll cost one year earlier than he might have otherwise. Nothing we can do about that. This does make him less likely to earn some performance bonuses, though - which could help out with next year's cap.