The good news for Brennen is that there is an open spot at #3 quarterback. He has every shot at making the team. Hasselbeck was a 6th round pick and it took him 4 years as a backup before he was ready to start. Tony Romo was undrafted. Hasselbeck is probably a more realistic comparisson than "Brady was a 6th round pick". Brady is the "once in a generation" exception. I would think that the Hasselbeck senario is what Zorn and co. are hoping for.... and there have been plenty of good QB's to come out of the late rounds or undrafted (at least for the NFC).
For comparison sake...
2007 Pro Bowl QB's (NFC)
Drew Brees -
NFL Draft: 2001 / Round: 2 / Pick: 32
Mark Bulger -
NFL Draft: 2000 / Round: 6 / Pick: 168
Tony Romo -
Undrafted in 2003
2008 Pro Bowl QB's (NFC)
Brett Farve -
NFL Draft: 1991 / Round: 2 / Pick: 33
Tony Romo -
Undrafted in 2003
Matt Hasselbeck -
NFL Draft: 1998 / Round: 6 / Pick: 184
Jeff Garcia -
Undrafted in 1994