Duke Silver wrote:Transmogrified Tiger wrote:This is a pretty good read: http://www.fangraphs.com/blogs/what-is- ... -rotation/
Especially worthwhile are the charts comparing 2016 xwOBA and xBA(calculated w/ Statcast data) with the actuals and how that compares with 2017. Hendricks and Lester have been getting similarly strong defense as last year, while Lackey has seen a decent dip and Arrieta has seen the defense behind him crater. Small samples, but it gives some hope that Arrieta and Lackey have better days in front of them.
Good stuff. I'm not even so sure that the defense is completely to blame. I think they are to blame some, for sure. They just haven't been as sharp defensively. And that's not something I expect to continue. There are a lot of really good defenders on this team. And I suspect they'll get their horsefeathers together.
But, if you look at the expected stats at https://www.xstats.org/ that Andrew Perpetua keeps, his expected stats are also based off of batted ball direction, which Baseball Savant's aren't. Savant's method only looks at launch angle and exit velocity. Pepetua's calculations have Lester's and Arrieta's xBA and xwOBA higher than Savant's, though not as high as their actual numbers. So I think another problem is that balls are just finding holes -- or finding where there usually are holes.
Add them both together, porous defense and finding holes, and then realize it's a small sample size and weird stuff can happen.
Yeah, I almost mentioned something to that effect. Sawed off bloop singles are going to hurt that xwOBA/wOBA disparity even if the defense wasn't to blame. Whatever the proportion is though, the good news is both seem likely to progress to the mean.