The Leafs did add Spezza, and I would expect that Matthews, Marner, and especially Rielly know what it is like to be a professional hockey player by now. Otherwise they shouldn't be getting paid like one. They've been in the league for 3+ years, many of which was with vets such as Hainsey, Marleau, Tavares, etc. They should know the amount and type of work they need to put in because if not, then Babcock, Hainsey, Tavares, Marleau, etc. have sucked at being leaders and they must have the steepest learning curves I have ever seen.
I'm not even worried about Matthews or Rielly at this point. Rielly has been inconsistent, but he's still getting used to Ceci and playing 25 minutes a night (which is 2-3 minutes more than he's used to). Considering he's still been a net positive player in a #1 role and should only get better as the season progresses, I would not worry about Rielly's play at this point. Same with Matthews. Sure he's had a couple of poor games since Tavares went down, but he's also taken over games on his own this year too. There are more times when he looks like someone worth his money than not, but he still needs to take it to that next level.
Marner remains my biggest worry. Outside of a few strong shifts, I don't think he's come close to looking like even a 9 million dollar player, never mind an almost 11 million dollar player. Sure he's racking up empty points, but he has not had a game which I would have called "good"... Maybe there was 1 or 2. And I really don't think it's a coincidence that Matthews started to do worse as soon as Marner started playing with him. The guy's game is built on playmaking and hustle, but right now, he does not have a consistent handle on either. To me, Nylander has been the better player all year. Even when Nylander was playing with lesser players, he's still making great plays without a ton of mistakes. Still wouldn't mind if he was a little bit more aggressive though.