You gotta keep in mind that Goff threw before the defender ran into Gurley. I don't think the plan was for Gurley to pick the defender. As McVay said, it was a simple slant-flat combination. Goff's read was that Gurley's defender wasn't in position to stop the slant. He was right. Unfortunately, Everett's defender was in position to prevent Gurley from getting to the slant. Refs blew the call.
I like the call, though. You get the ball in Gurley's hand on that slant, and all he has to do is shake one tackle to get the TD.