A Vegas insider RJ Bell explained in detail how lines move due to injuiries and inactive players when Gronk was listed as out on Thursday.
He said only about 32 players around the league other than QB's impact the line. Gronk moved it a "smidge" I think was his words, a half a point. I agree that the WR position has been mismanaged but i don't have much faith in Watkins.
I wrote this to let yah know, ain't no way in hell Sammy Watkins moves a line, nevermind 3 points. RJ bell is on twitter if you or anyone would like to get a solid confirmation on that.