Updated: Dec 12, 2021
On May 1st, 2021, Kyle Tucker was off to a rough start. His SLG was 0.610 and his wOBA was 0.259 and some fans were already jumping off the Tucker bandwagon. Two numbers told another story however and these two numbers let smart fans know that Tucker was about to get hot. Tucker's BABIP was 0.164 and his xwOBA was 0.35. That is right his EXPECTED wOBA was 91 points higher than his wOBA. that gap is ENORMOUS and was a sign for any Astros fans looking for validation of their belief that he was unlucky in April.
This morning I woke up thinking about wOBA and xwOBA. I know; fill in your own jokes here. The question I came down to is this:
What players had the greatest full season gap both positive and negative between xwOBA and wOBA. As a reminder, here is a short description of xwOBA from MLB.com and why it is potentially more valuable than wOBA. Quoting:
xwOBA is more indicative of a player's skill than regular wOBA, as xwOBA removes defense from the equation. Hitters, and likewise pitchers, are able to influence exit velocity and launch angle but have no control over what happens to a batted ball once it is put into play.
The thought I have here is:
Players with the largest positive xwOBA-wOBA gap would be the most underrated. People would significantly underestimate how good these players actually are by their unlucky results.
Players with the largest negative xwOBA-wOBA gap would be the most overrated. People would significantly overestimate how good these players actually are by their lucky results.
One may argue this is more about luck than how we rate a player. On the surface that is fair except even now people will talk about Tucker getting off to a "slow start." They generally don't just leave it as a unlucky start but assign some assessment in that he was below par in April. To me, that is a rating issue and not just a luck issue.
So who are the most underrated players? If I had absolutely no other data, these are players I would trade for or sign as free agents. Here are the players with xwOBA-wOBA gaps of >0.01. At what level does one really tend to think differently about a player?
I would say we
think a 0.260 average hitter is worse than a 0.280 hitter or
think a 0.475 slugger is worse than a 0.525 slugger.
Does that seem true to you too? If so, then a wOBA gap of 0.030 or more would seem to be significant and the top 13 on this list would be my most underrated position players list. For these lists I have only considered players with more than 300 PA to make sure this data had statistical significance.
So who are the most overrated players? If I had absolutely no other data, these are players I would trade away or never sign as free agents. Here are the players with xwOBA-wOBA gaps of < -0.01. Similarly, the top 13 players on this list have gaps less than -0.030 would be my most overrated position players list.
Calling the top 13 on this list overrated is not going to be popular. The names here themselves will bring a response- Arozarena, Semien, and Gurriel have won awards in the last few years. For me to be so bold as to say they are overrated- well, that is why you come here. We give you data based opinions. I won't apologize for an unpopular data based opinion.
I have called out one Astros player. How do the the rest of the Astros rank on this list? We said on April 30 that Tucker had a mind blowing 0.091 gap at the beginning of this article. How did is end up for the year?
From this analysis, however good you think Alvarez, Tucker, and Brantley were in 2021, you are likely wrong. They were better. Imagine this data with the age of Alvarez and Tucker and seeing it as a sign that they are going to be even better in 2023 and beyond. Be afraid MLB, be very afraid.
Similarly, Gurriel, Altuve, and McCormick were not as good as we probably thought they were in 2021. Gurriel is likely to be on the decline and Altuve is probably as well. Not what I want to say, but it is what the numbers would indicate.
In case you are curious about the others. I have the in between list at the end of this article.
There are some interesting synergies between this underrated list and the players on The Comebackers I wrote about. For those playing fantasy baseball, assuming we get to in 2022, maybe you should keep these in mind as potential sleepers.
As always, let me know what you think of the analysis here and let's talk about it in the forum.
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The list of players we probably rate correctly