Who says it has to be the HC?
For example, Dak improved monumentally between 2018 and 2019, and a lot of it was clearly because he shored up his mechanics. No more wild arm-punts, no more spinning out left when he felt pressure, etc. I give the credit for that leap to Tom House and Jon Kitna. Kellen Moore's infinitely-better-than-Linehan system no doubt helped Dak, but Moore didn't have anything to do with his huge step up in technique. And I wouldn't give a spit of credit to Garrett.
In general, it's weird how fans want to give the most credit for young players developing to the coaches who usually have the least amount of interaction with them. If you want to order the most significant factors in player development to the least, I'd say it goes:
-Themselves (experience with time, physical development, simple willingness to work hard and listen to instruction - sounds easy, but some guys like Trysten Hill don't even do it).
-Position coaches (day to day practice work, film review, technique instruction)
-Coordinators (system)
-Head coaches.
I'm not saying that HCs can't impact a player's development - I just wrote in another thread today about how Andy Reid has elevated every quarterback he's ever worked with. It's happened 5 separate times over 20 years with two different teams, so I think that's enough to rule out any confounding factors and say that it really is Reid. But HCs are the last factor I'd look at.
