You are dense sometimes.
xFIP, SIERA are better PREDICTIVE stats. Being a better PREDICITIVE stat means looking at the FUTURE.
FIP would be a better DESCRIPTIVE stat. DESCRIPTIVE stats tell you what happened THIS year. DRA would be another DESCRIPTIVE stat with some PREDICITIVE value. RA/9 would be a much better stat than ERA. All of these stats heavily favor Greinke.
I care more about the future when I'm talking about pitchers. So the stats you are mentioning are better at being PREDICITVE than DESCRIPTIVE. Hence you don't understand how I use them.
Listen to yourself. You know that these are all descriptive stats but, when it suits you, you portray them simply as predictive stats. Yes, perhaps they are BETTER predictive stats than ERA and the like but they are not simply predictive stats. They purport to be better performance measurements too.
Here is what Fangraphs says about x-FIP compared to FIP:
xFIP strips out some of this fluctuation to give you a better view of how well we think a pitcher pitched over a given period of time, while controlling for defense, batted ball luck, and sequencing, and also HR/FB%. In other words, we use xFIP to see how a pitcher might be expected to perform given an average HR/FB% because we do not expect pitchers to have much control over that number. In other words, x-FIP is simply an enhanced version of FIP that adjusts for HR rate. To quote Fangraphs, xFIP is "how well we think a pitcher pitched over a given period of time."
Plainlly, that is designed to be descriptive of performance---be a better stat(s) to measure true performance. Let's call it BETTER predictive, yes, but it purports to measure how well a pitcher pitched over a given period of time. That's what they say. Go to Las Vegas if you are only interested in using these stats as predictive. You need some balance here, let me suggest.
xFIP minus simply adjusts for league average on a 100 scale, like OPS+ does, as you know. Same deal as above re xFIP. That is why you cited xFIP minus when you claimed that Fister did not have a career year in 2014. Allegedly relevant to describing his 2014 season, so you said.
This is the definition of SIERA: "Skill-Interactive Earned Run Average {SIERA} estimates ERA through walk rate, strikeout rate and ground ball rate, eliminating the effects of park, defense and luck. SIERA accounts for how run prevention improves as ground ball rate increases and declines as more whiffs are accrued, while grounders are of more materiality for those who allow a surplus of runners." In other words, it purports to be a better version of ERA. Descriptive, not just predictive.
Don't know why you weasel around the obvious. Cite stuff as black and white when it suits you; ignore when it doesn't.
You should just say that under these stats Hendricks pitched as well--performed--as Greinke in 2015, as Fangraphs would say, "over a given period of time." In this case, the 2015 season. Of course, you are too embarrassed to say that. Doesn't jive with common sense. Now, you say just predictive, folks. Baloney.
I know you are not saying that Hendricks is as talented as Greinke nor saying that in PREDICTIVE terms will be as good in 2016. But, you should fess up and admit that these stats claim that their 2015 performance was basically identical in terms of "how well we think a pitcher pitched" {Fangraphs citation again} in 2015.
Yes, ERA has a luck factor. Baseball has a luck factor. I want to know what luck produced. I want to know how to compensate for luck. That's what newer stats purport to do. Great idea.
Game on: Very Hard hit groundball directly at the SS--double play. Good luck for the pitcher. Soft hit grounder-seeing eye 2-RBI single in the hole. Bad luck for the pitcher. We don't say, nice job for inducing the soft grounder. No, we say nice job for inducing the DP. That's baseball. I use ERA and x-FIP and FIP. I don't say ERA is unworthy of consideration, as you did when you said you "discount" ERA. That's just narrow-minded and too dumb for a smart guy like you.