Evolution of Pitching Rotations Under the Cap

2013 TEAM PITCHING ROTATION PERFORMANCE
TEAM IP K BB K/BB KPI WHIP KPI-WHIP FINISH
WA  121.0 307 96 3.20 2.54 1.07 1.41 1
EL  126.2 303 147 2.06 2.39 1.61 0.78 2
WW  121.2 261 104 2.51 2.15 1.64 0.51 4
HB  131.2 260 155 1.68 1.97 2.28 -0.31 3
DU  113.0 277 253 1.09 2.45 2.48 -0.39 6
KF  154.2 293 207 1.42 1.89 2.44 -0.55 5
BW  132.1 209 146 1.43 1.58 2.94 -1.36 8
IS  125.1 258 276 0.93 2.06 3.71 -1.65 7
WSEM  1026.1 2168 1384 1.67 2.11 2.32 -0.21
2013 Only 3 of 8 team pitching rotations have a sub-2.00 WHIP and a positive KPI-WHIP (37.5%). Top 4 pitching teams take the four playoff spots. #Chalk
2014 TEAM PITCHING ROTATION PERFORMANCE
TEAM IP K BB K/BB KPI WHIP KPI-WHIP FINISH
WA  169.2 423 110 3.85 2.50 0.96 1.54 1
EL  176.0 408 119 3.43 2.32 1.07 1.25 2
BW  180.1 441 139 3.17 2.45 1.30 1.15 4
FS  139.2 360 168 2.14 2.58 1.80 0.77 5
ON  126.0 272 90 3.02 2.16 1.41 0.75 7
WW  115.0 233 106 2.20 2.03 1.70 0.33 6
HB  158.2 332 178 1.87 2.09 1.89 0.20 9
KF  139.0 296 181 1.64 2.13 1.94 0.19 3
WO  133.1 208 271 0.77 1.56 3.38 -1.32 8
IS  93.1 165 171 0.96 1.77 4.20 -2.43 10
WSEM  1430.2 3138 1533 2.05 2.19 1.82 0.38
2014 8 of 10 team pitching rotations have a sub-2.00 WHIP and a positive KPI-WHIP (80%). Top 4 pitching teams make playoffs, but the number 8 pitching rotation plays its way in. #Darkhorse
2015 TEAM PITCHING ROTATION PERFORMANCE
TEAM IP K BB K/BB KPI WHIP KPI-WHIP FINISH
RC  169.2 409 116 3.53 2.41 1.14 1.27 2
WA  145.1 337 84 4.01 2.32 1.12 1.20 1
SY  169.2 360 99 3.64 2.13 1.46 0.67 8
FS  172.2 407 183 2.22 2.36 1.69 0.67 3
WO  167.2 343 161 2.13 2.05 1.56 0.49 4
EL  152.0 318 179 1.78 2.09 1.96 0.13 6
HB  176.2 367 181 2.03 2.08 2.06 0.02 6
IS  157.2 325 195 1.67 2.06 2.06 0.00 5
WSEM  1310.0 2866 1198 2.39 2.19 1.64 0.55
2015 6 of 8 team pitching rotations have a sub-2.00 WHIP (75%), but all 8 teams post a non-negative KPI-WHIP (100%). The number 8 pitching rotation plays its way into the playoffs along with the top 2 and numbers 4 and 5. #Parity
Evidently, the performance of pitching rotations around the league has come closer and closer over the years. There is no bad rotation to speak of from the 2015 season. Today's number 8 rotation would fit in the top 4 two years ago. Every staff is now dealing more strike outs than they are allowing walks or hits, and there is no longer a single team far removed from the numbers put up by the rest of the league. This has created a world where the eighth best rotation is good enough to be a playoff team. Every rotation is now throwing in playoff contention. For a deeper look at parity, just compare the average run differential of playoff teams and the shrinking divide of runs allowed over the past 3 years:

2013 2014 2015
Average Run Differential of Playoff Teams   82.8 48.6 27.4
Difference Between High & Low Runs Allowed   253 266 101
Standard Deviation of Runs Allowed   76.8 78.6 33.7
Average run differential of playoff teams reduced by 58.6% in 2014 with the introduction of the talent cap, then reduced by another 56.4% in 2015 with the salary cap. Read: "Blowouts and domination are dwindling." The salary cap also closed the gap between the highest and lowest runs allowed by a pitching rotation, decreasing it to less than 40% of either preceding year. The standard deviation of runs allowed across the league saw similar reduction by nearly 60% from the previous seasons. #GettingThere