Hackett has support from his NFL peers. Two of the NFL’s top coaches are rallying around embattled Denver Broncos head man/offensive play-caller Nathaniel Hackett, whose rookie foibles have spawned relentless national mockery. Hackett’s sympathizers include his upcoming opponent, 49ers HC Kyle Shanahan. “It’s not always about getting the play in. You need receiver substitutions, you need the quarterback getting to the line. There’s so many things that go into it,” Shanahan said Wednesday of his own experiences, via 9News’ Mike Klis. “You’re always responsible for it but it takes a whole team to do that the right way and early…