Both are good players. Gurley use to be a great player though and is sliding quickly because of health. He just can't do it anymore, but he gave the Rams a few great years so no hate, just objectivity.
Goff on the other hand has to deal with a the lack of a multi-purpose runningback threat to make a big play and a below average offensive line. These obstacles are hard to overcome.
The bottom line is Goff will be good again once the elements around him are fixed. I do not think Gurley will ever be an above average starting RB again because of his knees.
