That stat assumes stability in launch angle and speed off the bat, neither of which is mentioned as a stable trait in batters. The article states "Orioles third baseman Manny Machado produced a .335 wOBA in 2016. But based on the quality of his contact, his xwOBA was .357."  Dis Machado regress because of poorer launch angles or exit velocity, better defense as his number of singles dropped or other factors? Predictive exercises can be entertaining, but might be of the same usefulness as the abduction/adductor   machine

  On 1/20/2018 at 3:25 AM, old nurse said:

That stat assumes stability in launch angle and speed off the bat, neither of which is mentioned as a stable trait in batters.

Zactly.  In order to be meaningful, the stat would have to correlate launch angle/exit velocity with pitches, at the least (pops up four-seamers, chops curveballs, etc.) Then, you would also have to learn whether angle/exit stabilizes over a hitter's career.  Do we predict off of a young player's second half, whole season, minor league record?

Also, is the stat a good predictor at all?  Eyeballing the lists above against baserunning speed, it looks like it might underrate speed's effect on hitting performance, especially for those who hit grounders frequently.

Still, an interesting approach with potential.

Thanks for the post, Thrylos!

It does not factor in a batter’s speed as a skill.

xwOBA is concerned only with what happens just after the ball leaves the bat, and what the hitter does once he leaves the box doesn’t change it all. Of course, a speedy batter is much more likely to turn a gapper into a double or a triple than a slow batter is. Any difference as a result of speed should not change.

Another factor that might account for differences in xwOBA and wOBA is ballpark factors. xwOBA doesn’t care about the ballpark. Since the Twins are playing in Target Field any difference due to park should not change.

The last of course is luck. This is what xwOBA hopes to measure. Which batters hit the ball better than their numbers indicate? They might expect that their numbers did not match their ability and can expect that they would this year.

I also think a fourth factor might be a hitter’s spray chart. How easy is it to shift the defense in areas where the player consistently hits the ball hard?

What does it mean for those Twins?

Is Buxton difference mostly due to good luck or his baserunning skill? How about Mauer? How much is bad luck and how much is slow baserunning?

How about Mauer vs. Rosario? Rosario’s line drives are spread from foul line to foul line. Most of Joe’s are left field to center field. Which player is easier to shift against? Wouldn’t that effect this number?

It would be awesome to have a measure bad and good luck to help determine a player’s skill level? Baserunning is a skill. The ability to hit the ball to all fields is a skill. I don’t think this number factors those skills out.

Good post Thrylos. Always more fun this time of year to attempt predictive stats than descriptive

Well, just based on xwOBA-wOBA, and just about the whole team declining, I guess it could be a long season. Damn. I might have to pretend I never read this.

  On 1/20/2018 at 4:11 PM, jorgenswest said:

It does not factor in a batter’s speed as a skill.
 

Likely why the first list has three slow runners, an extremely small sample size and the closest number to 0 of all the data points ... Meanwhile the top four negatives are arguably the four fastest players on the team that have a reasonable amount of data to draw from