Tangotiger Blog

Wednesday, September 25, 2024

Runs Above Average

It is very (very very) simple to figure out Runs Above Average (RAA) for a pitcher. I'll use Paul Skenes as the example.

Take the league average ERA (4.086) and subtract our pitcher's ERA (1.992). That makes Skenes 2.094 runs per 9 IP better than league average.

Since Skenes has 131 IP, we take the above number (2.094/9) and multiply by 131 to give us +30.5 runs above average.

That's it. That is Runs Above Average using ERA-only. That figure for Skenes is 4th highest in MLB, behind Sale (+34 runs), Skubal and Wheeler (+33).

Now, you may be asking: what about park factors? Baseball Reference has Skenes as pitching in slightly batter's parks. So, that simple league average of 4.086 is actually too simple, since that figure is the same for all pitchers. We know that can't possibly be true. Skenes also faces tougher competition than average. Skenes supposedly has weaker fielding support than others. When you make all these adjustments, Skenes actually ends up being +41.5 runs above average. Remember, unadjusted he was at +30.5 runs above average. So, the adjustments gives him an extra +11 runs. That's right, his 1.99 ERA is actually NOT giving him enough credit.

Since Baseball Reference is terrific in how they share their data, it's really quite simple to compare the ERA-only RAA to the fully-adjusted RAA they provide.

On this chart (click to embiggen), on the x-axis is the ERA-only RAA. If you don't want anything adjusted and you just want to rely on ERA, then just look at those numbers.

The y-axis is the bonus (or deduction) you have to apply to your pitcher to account for the context that they end up pitching in. Skenes for example is in the right corner, at 30; 11. That means his ERA-only RAA is +30 runs, and he has a +11 run bonus for his context. So, he's worth +41 RAA.

Some pitchers get FAR more bonus than that. Hunter Greene gets +19 runs of bonus for his context. That means his ERA is really clouded, practically Coors-like in its effect. So, he's +20 runs for his ERA-only and another +19 runs for the context, for a total of +39 RAA.

Erick Fedde is +13 for his ERA-only, and another +17 for his context, giving him +30 runs above average.

We can compare Cy Young candidates Cole Ragans (+17, +10) to Logan Gilbert (+18, -10). You see, both are very similar based on their ERA. But according to Reference, Ragans faced a tough context, while Gilbert had a pretty easy context. That's a 20 run gap between the two in terms of their context. So Ragans ends up being +27 while Gilbert is only +8.  In other words, instead of Ragans being 1 run behind Gilbert, he's 19 runs ahead, all because of the 20 run difference in their context.

Now, there's no question that if you are a Mariners fan, you will disagree, and a Royals fan is quite happy. That's unfortunately how these contexts gets interpreted: how does it affect MY player.

Chris Flexen is one of the worst pitchers in baseball using ERA, at -18 runs.  But Reference says he also had one of the toughest pitching environments to the tune of +17 runs.  So overall he ends up being practically league average at -1 runs from average.

Did Chris Bassitt have an ordinary season (-1 RAA)?  Or did he have one of the easiest contexts in all of baseball (-15 runs) so that he actually had a disastrous season (-16 RAA leading to -0.1 WAR)?

By ERA, Bassitt is 17 runs better than Flexen.  By fully-adjusted Reference method, Flexen is 15 runs better than Bassitt.  One had an average season, one had a disastrous season. And which pitcher had which is based on whether to fully trust ERA or to fully accept the adjustments.

Reference lays it all out there for you so you can see what they are doing. You either buy it or you don't. But the transparency is something to be commended.