For starters:
Dez was hurt, and wasn't right after his return.
The LG position was not held down by Leary
RB was not as good.
On Defense:
Terrell Mclain got hurt
Scandrick missed the season
Greg Hardy drama
Offense:
So four extra games of Dez
LG being Leary instead of La'el, but every other member of the Oline was still the same.
McFadden averaged 86.7 rushing yards per game after he took over as the full time back. Our rushing game was really good, had the 9th most yards in the league despite having only the 18th most attempts.
Defense:
McClain got hurt at a position that was manned by Nick Hayden the year before.
Had both Rolando and Lee that year
Greg Hardy played really well for us
Scandrick was replaced by Byron, who was the 2nd highest rated 1st round rookie that year
We were 3-1 with out starting QB, and 1-11 without him.
So tell me. The 9 game upswing from 2015 to 2016, who made the most difference?
Was it Collins to Leary?
Was it 1,000 yard rusher in 10 starts McFadden to Zeke?
Was it getting old Scandrick?
Four more games of Dez?
Getting McClain back?
Losing Hardy's 7 sacks?
Or going from the worst passing DVOA collection of three QBs to a good QB?