## Which Royals Pitchers have deceptive ERAs?

A couple days ago, I proposed a new stat called Isolated ERA, and got some great feedback. I've now modified the concept to just look at Runs (as opposed to Earned Runs) and utilize the calculations already made with the RE24 stat.

Here is my updated definition, along with the calculated stats for the Royals Staff, and some interesting (at least to me) conclusions that can be drawn.

Isolated Runs Allowed per 9 IP (iRA9)

The goal of Isolated Runs Allowed per 9 IP (iRA9) is to eliminate the effects of the rest of a pitching staff on an individual pitcher’s runs allowed stats. When a pitcher leaves runners on base that they are "responsible for", whether or not the next pitcher(s) allows these runners to score no longer influences the original pitcher’s runs allowed. Their iRA9 is adjusted based on MLB average performance for how likely these runners score. Similarly, relief pitchers are credited for inherited runners they prevent from scoring, but still held partially responsible if allowing them to score (again adjusted for performance compared to MLB average).

Calculation:

(ARI* IP - RE24) / IP * 9

ARI = MLB Average Runs per Inning (total Runs / total IP)

IP = Innings Pitched (converting to fractional values, i.e. 5.6667 instead of 5.2)

RE24 = runs above average by the 24 base/out states (see full definition & example here)

How to look at the data:

iRA9 is similar to ERA or RA9 (runs allowed per 9 IP) in that it looks at the actual results for a pitcher (as opposed to theoretical projections based on peripheral numbers) and presents these numbers on the scale of Runs per 9 Innings Pitched. The key difference is that iRA9 is based solely on the results while that pitcher is in the game, and not the results of the pitchers to follow. Thus it eliminates the effect of the rest of a pitching staff on an individual pitcher’s numbers, so represents a truer indication of that pitcher’s results.

iRA9 can also be compared to RA9 directly to identify pitchers that have inflated or deflated RA9 numbers (and therefore likely ERA as well) based on the performances of other pitchers on the staff. For example, if a pitcher’s iRA9 is much higher than his RA9, then he is benefiting from other pitchers lowering his RA9/ERA by stranding the runners he is responsible for using the conventional method of scoring. Similarly, if a pitcher’s iRA9 is much lower than his RA9, his RA9/ERA is being hurt by above average runs being scored by runners left on base. Relief pitchers can also have a low iRA9 by consistently stranding inherited runners.

Looking at the Royals:

I calculated iRA9 for all Royals pitchers following the game on 6/17:

 Pitcher ERA RA9 iRA9 Mitch Maier 0 0 -0.19 Felipe Paulino 1.67 1.91 1.66 Jonathan Broxton 1.69 2.36 2.15 Vin Mazzaro 2.57 3 2.38 Aaron Crow 2.76 3.07 2.41 2.36 2.36 2.66 Louis Coleman 3.15 4.05 2.96 2.39 2.39 3.28 Kelvin Herrera 3.22 3.47 3.32 3.9 4.23 3.89 Nathan Adcock 3.12 3.46 4.10 5.73 5.73 4.31 5.05 5.17 4.90 Luis Mendoza 4.69 5.34 5.18 Roman Colon 4.91 4.91 5.29 Greg Holland 3.86 3.86 5.54 Luke Hochevar 6.27 6.4 5.83 3.38 3.38 6.00 Jonathan Sanchez* 5.93 5.93 6.09 9 9 9.00 Jeremy Jeffress 0 0 21.41

And comparing iRA9 to RA9:

 Pitcher ERA RA9 iRA9 iRA9-RA9 Jeremy Jeffress 0 0 21.41 21.41 Tommy Hottovy* 3.38 3.38 6.00 2.62 Greg Holland 3.86 3.86 5.54 1.68 Jose Mijares* 2.39 2.39 3.28 0.89 Nathan Adcock 3.12 3.46 4.10 0.64 Roman Colon 4.91 4.91 5.29 0.38 Tim Collins* 2.36 2.36 2.66 0.30 Jonathan Sanchez* 5.93 5.93 6.09 0.16 Will Smith* 9 9 9.00 0.00 Kelvin Herrera 3.22 3.47 3.32 -0.15 Luis Mendoza 4.69 5.34 5.18 -0.16 Mitch Maier 0 0 -0.19 -0.19 Jonathan Broxton 1.69 2.36 2.15 -0.21 Felipe Paulino 1.67 1.91 1.66 -0.25 Bruce Chen* 5.05 5.17 4.90 -0.27 Danny Duffy* 3.9 4.23 3.89 -0.34 Luke Hochevar 6.27 6.4 5.83 -0.57 Vin Mazzaro 2.57 3 2.38 -0.62 Aaron Crow 2.76 3.07 2.41 -0.66 Louis Coleman 3.15 4.05 2.96 -1.09 Everett Teaford* 5.73 5.73 4.31 -1.42

A few things jump out here:

1. Holland’s ERA is extremely deceiving (lower than his performance indicates it should be), as he’s been bailed out by the other relievers (maybe a nice steak dinner is in store for Crow and Collins?).
2. Mijares is also benefiting, although not to quite the extreme as Holland. A sell-high candidate?
3. Hochevar can’t catch a break, as his RA9 is inflated by over a half-run based on the relievers following him. I think much of this can be explained by the fact he’s gotten bombed early so many times that it is usually long-relief guys coming in, as opposed to late-inning relievers more adept at stranding runners.
4. The extremes on both sides are based on small sample sizes, but looking at their outings they do make logical sense (e.g. in 3 outings Jeffress allowed an inherited runner to score, but left 4 runners that were stranded by Crow/Mijares; in 3 outings Teaford stranded 2 runners, but the only runner he left on base scored on a HR given up by Herrera)

Thoughts?

This FanPost was written by a member of the Royals Review community. It does not necessarily reflect the views of the editors and writers of this site.

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