Overall, Dak is certainly a better thrower than Cooper. That said, his tendencies have made it harder for everyone around him which in turn makes it harder for him. Dak was leading the NFL in tight window throws. Cooper just throws to wide open guys. Its not a coincidence. Its the same group of receivers.
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Get it out quick.
Good point about guys looking open with Rush.
Rush doesn't put much on the ball, but he finds the open receiver, gets the ball out quicker, and hits guys on the move.
With Dak it's so many stick routes, so many receivers catching balls while they're standing somewhere. And a real big problem, so many balls that let the *next* guy in the zone close on the play. That's where Dak gets into trouble - not the guy covering the receiver, but the covering the space the receiver is running into, and closing on the catch.
Being slow makes it harder on everyone: QB, receivers, and oline.
When Kitna coached Dak that one offseason, the mantra was "Let 'er rip!" And when Dak did that, he had that incredible start to the season. Probably a mix of Dak's play and the defenses we played against. But that really showed what had been missing in Dak's game, and what's missing when he's not playing well too.
A tick fast or a tick slow isn't the most obvious thing, but it makes a huge difference.