I wanted a quick post to clarify how I came up with my tiers from my previous posts. I used a k-means clustering method with k = 4 for RBs and WRs and k = 5 for QBs. These values of k were the smallest that achieved a ratio of between cluster sum of squares and a total sum of squares > 80%.
Without going into too much detail about how a cluster analysis works, each player is assigned to the cluster who’s center is closest to that player’s stats. Thus, a player could be very close to being in different clusters. Below are the cluster centers for each position:
|
QB Tier Average
|
||||||||||
|
Tier
|
Comp
|
Att
|
Yards
|
TDs
|
Ints
|
Rush Att
|
Rush Yds
|
Rush TDs
|
Ratings
|
Pct
|
|
1
|
25.67
|
39.76
|
322.03
|
2.56
|
0.93
|
5.74
|
6.59
|
0.28
|
149.13
|
64.56%
|
|
2 – DT
|
14.75
|
25.22
|
185.65
|
1.34
|
0.69
|
13.11
|
63.43
|
0.77
|
132.28
|
58.46%
|
|
2 – Pro
|
20.06
|
32.94
|
250.89
|
1.82
|
0.88
|
6.63
|
11.22
|
0.29
|
137.75
|
60.90%
|
|
3
|
16.10
|
27.89
|
196.07
|
1.30
|
0.87
|
5.86
|
5.60
|
0.19
|
125.98
|
57.73%
|
|
4
|
11.89
|
21.71
|
139.17
|
0.86
|
0.77
|
6.76
|
13.31
|
0.22
|
114.56
|
54.79%
|
|
Rushing Tier Average
|
|||||||
|
Att
|
Yards
|
TD
|
Avg
|
Rec
|
Rec.Yds
|
Rec.TD
|
|
|
Tier 1
|
22.31
|
127.17
|
1.26
|
5.70
|
1.75
|
16.07
|
0.09
|
|
Tier 2
|
17.26
|
89.78
|
0.82
|
5.20
|
1.54
|
13.74
|
0.07
|
|
Tier 3
|
12.71
|
61.98
|
0.56
|
4.88
|
1.28
|
11.04
|
0.06
|
|
Tier 4
|
9.01
|
38.31
|
0.35
|
4.25
|
0.97
|
7.98
|
0.04
|
|
WR Tier Average
|
||||
|
Rec
|
Yards
|
TD
|
Avg
|
|
|
Tier 1
|
6.64
|
100.43
|
0.82
|
15.13
|
|
Tier 2
|
4.83
|
69.30
|
0.51
|
14.35
|
|
Tier 3
|
3.53
|
47.57
|
0.34
|
13.46
|
|
Tier 4
|
2.60
|
29.54
|
0.19
|
11.35
|
The names of each cluster are arbitrary. I decided to call each a tier due to each cluster having a distinct production gaps. Dual threat QBs were almost universally grouped into a single tier (Tier 2 – DT) unless they also threw for around 300 yards. Only on eight occasions did a Tier 1 QB also rush for more than 50 yards per game. Kyler Murray, Johnny Manziel, Robert Griffin III and Marcus Mariota all won the Heisman when accomplishing that feat. The other QBs to have done this are Trevone Boykin (twice), Shaun King, and Chase Clement.
I considered most dual threat QBs as Tier 2 players due to their yardage output similarity of Tier 2 – Pro Style QBs. Both groups produced approximately 250 yards of total offense per game and about 2 TDs per game. Dual threat players reach these numbers in a slightly different manner than more traditional pro style QBs.