IMO the re-injury to RG took his head out of the game. His left leg is more important for throwing the ball but he didn't have the experience to adjust. The early tweak took away the run and messed up his throws but it wouldn't be as much of a factor with a veteran. Compare it to Roethlisberger last year vs Denver. #7 was all but a cripple in that game yet his arm was still a threat.
Also, what alternative does a home team have when playing on natural grass two weeks in a row?
Blaming the field on injury is weak. Players get the same injuries on every type of surface. For a while synthetic turf was blamed for all kinds of injuries.