The defense has a part in it, but that isn't what I'd say is the main part. Greer simply takes too many damn penalties. During 17-18 and 18-19 Greer played 32 games with the Avs. During that time he averaged 4.37 penalties per 60 minutes. With no filter, that is 14th worst in the NHL during that span. If you make that filter 50 minutes... it is 4th worst in the NHL during those two seasons and none of the players above him played more. If you make that just 18-19... Greer takes the most penalties per 60 in the league. You simply can't have a 4th liner in today's NHL that does that. Their job is to grind, play solid defense, don't do anything stupid, and protect players when needed. Greer's defense is already an issue, but add in him being counted on to do something stupid and cause the team to go on the PK just killed any chance he had with Bednar. No NHL coach will stand for a 4th liner that takes a bunch of dumb penalties.
To put into context how bad Greer's numbers are... in 18-19 minors per 60 was 4.47. Brett Richie was the highest regular NHL player at 1.89 and he was followed by Roussel at 1.88. NHL coaches are driven nuts by numbers approaching 2... you get over that you get in the doghouse... you double it... you'll never see the NHL. As long as Greer does that, he'll never sniff a full time job. If he cleaned it up, I think he can be a 4th liner somewhere still.