One thing I'm sure McCarthy learned at Green Bay (was before his time, more of a Ron Wolf/Ted Thompson thing), was to draft a developmental QB to back-up your main guy and then trade him if your main guy stays effective. It doesn't mean you are going to hit on every single one of them, but they hit on more than they missed.
Brett Favre (time in Green Bay 1992-2007)
1992 9th round Ty Detmer - 54 games, 25 starts in NFL career
1993 5th round Mark Brunell - 193 games, 151 starts (traded to Jacksonville for 3rd & 5th round picks)
1996 7th round Kyle Wacholtz
1997 7th round Ron McAda
1998 6th round Matt Hasselbeck - 209 games, 160 starts (traded to Seattle to move up in the 1st round)
1999 4th round Aaron Brooks - 93 games, 90 starts (traded to New Orleans with another player for a 3rd round pick)
2002 5th round Craig Nall
2005 1st round Aaron Rodgers
2008 2nd round Brian Brohm
2008 7th round Matt Flynn - 53 games, 7 starts (left Green Bay to sign big free agent deal with Seattle)
2012 7th round B.J. Coleman
2015 5th round Brett Hundley - 18 games, 9 starts (traded to Seattle for a 6th round pick)
In that same period (1992 to now). the Cowboys have drafted the following QBs:
2001 2nd round Quincy Carter - cut
2009 4th round Stephen McGee - cut
2016 4th round Dak Prescott - Thank God
2018 5th round Mike White - cut