Auston Matthews is arguably a top 5 player in the National Hockey League today and signing his next contract this off-season proved his commitment to the Toronto Maple Leaf organization, something Willam Nylander has trouble showing with his contract negations, and it seems not everyone likes Nylander's laid back attitude all the time.
Having a laid back disposition can be an asset for sure, but being that way at all times can send the wrong type of message to be sure and it seems like Matthews isn't a fan of Nylander's ‘chill' demeanour.
It sounds like he thinks that a little bit more work would be an asset to the team. Either way, I think both players could learn something from each other. Matthews could teach Nylander to take the game more seriously and Nylander could teach Matthews how to relax a little bit during the season.