I'm a big fan of Bryce Petty. In a write-up on Petty I found this interesting:
"Whitfield said the latter is sort of a silly case to prove. According to his research, 74 percent of NFL snaps in 2014-15 came with the quarterback in shotgun formation. Only the Baltimore Ravens' Joe Flacco, he said, took the bulk of his snaps under center."
http://espn.go.com/blog/nflnation/po...baylor-pro-day
Throwing from the shotgun is only one aspect. Going through progressions is another. Petty needs to be able to read defenses.