You may have read a piece by Mike Sando today that discussed a philosophical change in pass routes versus the blitz. You may have also noticed that Sando linked to a Grantland piece by Chris Brown (no, not the one who slaps women around) which went into further detail on the matter.
Both articles are worth a read and provide some insight into why Alex Smith might be playing more mistake-free football this year under new coach Jim Harbaugh.
The premise of the piece is that Brown noticed the 49ers receivers are not adjusting their routes versus the blitz, but rather that the scheme has built-in hot routes by design. This means Alex knows if the blitz comes from the middle, he throws to the slant route (which is part of the play call even if there isn't a blitz and will be run regardless).
If Smith reads blitz, he reads shallow-to-deep. He can throw the three-step route to the area vacated by the blitz, or if his protection holds he can glance at the next level for a deeper throw. The key to this is that Alex and his receivers don't have to be mind-melded at the line of scrimmage, knowing where the receiver will break his route-off and Alex will throw.
Going back to what Urban Meyer said about Smith, this strategy (which is used in other systems outside of San Francisco, as noted by Brown...it's not just an "Alex Smith" scheme) gives Smith the confidence of knowing where the ball goes without having to change that plan at the line. This means he knows what to do and doesn't have to figure it out post-snap.
Give a read and learn something you may not have known.