Yes, but Marner totally disappeared in round 2 against Florida. Also, if I'm not mistaken, Marner has always been a poor playoff performer in previous yrs, with the Leafs!!
Management and coaching are what the Leafs need to focus on. Florida beat Toronto because of two things, lack of secondary players and they were out coached.
Many GMs' have the same challenge, they have a few highly paid stars and need to build a team around them. There is another thread that showed the top paid players between Florida & Toronto. The difference was only 4 million$. That's not much of a difference. The Florida GM (and other GM's) are more skilled at building a team to support those key players, and that is where Dubas has failed. Dubas even tried to change the "grit" factor at the trade deadline and that only resulted in winning the first round (against a tired Tampa team that limped into the playoffs).
Per the actual series, the Florida coaching staff designed a game plan on shutting down the core 4 and Keefe was unable to counter that strategy.
A stronger supporting cast and a reliable goalie (I cannot understand why they thought Murray was the answer!!!), perhaps a new coaching strategy and this group of men could bring it all home.
Put this core 4 on any other team (replace their core 4 stars), and that team is a legitimate cup contender.