I think this was a simple matter.
CJ Anderson was the hot hand. Gurley is the home run hitter.
I don't know why Gurley messed up on those two passes; maybe it messed with his head.....but I doubt it.
The Saints did exactly as the Rams did: they were determined to shut down the run and force the other team to pass. And because of his style, CJ Anderson fit the bill better in this game.
Clearly McVay figured that the Rams were going to have to throw the rock and that runs were going to be the 3 yards and a cloud of dust variety. That is CJ Anderson and not Todd Gurley.
I'd lay a couple of bucks on the green that Gurley is going to be front and center in the game plan for the Pats, and that he'll have himself a fine game.