Both Stafford and Ryan started from game one as rookies to begin with, as opposed to game 11.
The same size is too small for the aggregate averages to mean anything. You need to look closer, such as Matt Ryan had a QB rating over 120 in two of his first three starts. His second game, against one of the best defenses in the NFL, was bad enough it distorts the three game average view. Goff, on the other hand, has had two bad starts and one good one, against one of the worst defenses in the NFL.
I think everybody knows Stafford was pretty dismal as a rookie. So if that's the hope you have, that's fine. I personally am hoping that eight years in we'll be able to look back and see Goff was significantly better than Stafford over his first eight seasons. He better be given the investment,.