Nothing substitutes actual game speed and game time reactions. Nothing. Don't let anyone convince you otherwise. If a QB is returning to action with a team he has played with for some time in actual games it helps. But on a new team with an entire new roster having never played actual games in real time, it takes games to get some chemistry going. Practice doesn't do that. Even preseason doesn't do that. How many times have you watched teams with a new QB come out looking flat at the beginning of the NFL regular season? And we're talking about a QB who will not have played in an actual NFL game in almost two seasons.