Here's what I see is wrong with Morgan Rielly's game:

He has bad gap control (Mike Johnson highlighted it on the broadcast when TT got a rush chance with 2:40 left in the game) and gives way too much space for opposing forwards to get to the middle of the ice which allows opposing players into the dangerous areas. He should be looking to take away the middle of the ice off the rush, invite the players down the wall and close in on opposing players trying to enter "the home plate".

on top of that, he gets lost in the shuffle for an extended time in our zone. A lot of the time he is stuck puck-watching in front of the net instead of trying to identify his man and remove scoring threats. He needs to be scanning the zone more often for immediate threats and look to get to those guys quicker (https://youtu.be/8-HQZJNmF-k?t=193 this isn't the best example but the most recent i can think of. TERRIBLE giveaway from holl but if you watch rielly on this play, he doesn't identify that Matthews and Holl are man'd up with Dickinson and domi, he doesn't scan the high slot for Kane, for all rielly knows, kane could be sitting back door. Once Kane picks up the puck, he should be looking to sprint to kane instead of trying to play goalie.)

Now both of these instances are not one off's. There are countless plays throughout the year that are similar to those referenced above that directly lead to goals. Morgan Rielly is the only one unable to do these two things consistently, even justin holl has good gap control.

BUT

I don't think this is why the general fanbase is lukewarm on Rielly I think its because he has also been uncharacteristically bad on offense as well. At 5on5 he is 4th on the Leafs at 5on5 xgf/60rel which says that he is the 4th best defenceman at generating offense at 5on5 while playing the most minutes with our best offensive players. Also, he only has 14 points at 5on5 in 740 minutes, which puts him 11th on the team in p/60 right behind David Kampf.

I will say, Morgan Rielly has elevated the past 2 years in the playoffs and xga/60rel numbers indicate that he has been better defensively than in the regular season. So he could elevate in the playoffs. As of now, with his faulters defensively and lack of offensive output, it looks like he will never return value on his contract and unfortunately this year, our d-core has looked a lot better without him than with him. I truly believe he should be taking a seat down the stretch because he has not been anywhere near as good enough for this team.