The Patriots might know, but how would we know? Because he's played slightly above mediocre in garbage time against 3rd string D's? He wasn't impressive when I saw him in camp, though I understand he played better towards the end. O'Connell was the future when we drafted him, and Mallet too - and people actually thought Cassell should stay and Brady should go, and people thought Hoyer was legitimate before we outright cut him....etc, etc. Heck Matt Gutierrez killed it in the preseason.
We don't know anything about the guy other than the Patriots value him as a legitimate backup QB, just as we did every other player I have just mentioned who is no longer with the team.
JG might have the best preseason stats out of them - but its premature to suggest he is or is going to be an NFL caliber starting QB. The people we are comparing him to have had little to no success in the NFL, particularly compared to the player people want him to replace.