I think maturity is a misused word. I believe it is entirely due to the age of our players, but I think it's used as a replacement for: drive, will to win, competiveness, consistency, leadership, and a bunch of other stuff. If my office and my beer league hockey teams are any indication, actual maturity doesn't mean squat. I play with guys who are natural born leaders and don't give a single damn about winning a hockey game. I play with young guys who have to win. Actual maturity means nothing.
Of the words that get confused for maturity, I think drive and its cousin "will to win" are the most important ones. Some people are born hungry to win and others learn to be hungry. Looking at teams around the league, I think Crosby and the Penguins were born hungry and lost their drive a little bit after their first cup. (The team struggled to get contender level depth for a few years, but that's beside the point). Crosby and Malkin were playoff heroes almost the moment they touched the ice. Other players didn't develop that drive until they'd been in the league for a long time. Ovi was a playoff superstar from minute one, but as he got hungrier and hungrier he developed a stronger two way game. That team always felt like it had to learn how to "want it". Some guys are born with the hunger, some take longer to get there. Some keep it after a win, some take a few years to get it back.
When I look at the Leafs I see Matthews as a guy who is hungry. I think he wants to win deep, deep down, and that's why we're seeing him blossom this year despite the team's relative struggles. I think Rielly wants to win. I think Marner wants to win. Kappy would rather gnaw his leg off than lose. The whole team are competitive guys and I certainly don't mean to disparage the players who I didn't list, but I think that we all want to see the team as a whole take the next step in finding their drive. Every team and every player will be different in when/how they get there. Frankly, losing to the Bruins two years in a row doesn't seem to have impacted our guys in the regular season so far, but we will see if they've learned anything for the playoffs. It's hard to draw parallels between former cup winning teams taking the regular season easy and the Leafs with our lack of success, but I do think that it's tough to judge maturity in the regular season. I think the team has been excellent and highly competitive under Keefe and are playing like a clear-cut playoff team. A lot of that is just based on the strength of the roster, but it's hard to argue with results. I place almost no stock in how a team performs after a goalie lets in a fistful of stinkers, you'll never find a team who plays hard to come back from a 6-2 deficit every time.
The playoff series that I watched last spring showed a Leafs team that was playing hard and looked hungry, but who suffered from bad coaching, a suspension to a key player, and were victimized by a ridiculous powerplay. Of all the things that caused us to lose that series, I don't think that drive and will to win were the culprits. Obviously I want to see more effort and drive, but it's not something that concerns me about this team. As for the regular season, I think that we pay far too much attention to individual games. We haven't been starting on time lately, big deal. That's a micro trend that should not be extrapolated to team-level discussions about drive and will to win. The team has been 1000x better at starting on time under Keefe than Babcock, so a tiny slip here and there should not be cause for alarm. I hate to be flippant when we aren’t even in a playoff spot, but the playoffs are really the only time where drive and will to win really matter.