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Digging Deep Series – “Buy Low (Hot-Rod), Sell-High (Lemons) Pitchers”

Digging DeepTo use StatCast data for deep analysis on pitchers, I started with the simple difference between wOBA and xwOBA. The difference between actual results (i.e. wOBA) and expected results (based on the batted ball data for their pitches, i.e. xwOBA) would provide a crude high-level method to identify overachievers or underperformers thus far in the young season. Again, the disclaimer of ‘small sample size’ applies, but anything that moves the needle one way or the other should be considered when making roster decisions.

Below are a some “Hot Rods” whose actual performance is below league average but whose expected underlying metrics suggest above average performance (and vice versa for the lemons). Also, I selected some lesser known names. Although Blake Snell may appear on a Hot Rod list, we already know that he is a stud so he would not be listed.

Some quick housekeeping before we dive in. For all this talk about wOBA and xwOBA, a reasonable question for a reader to ask is whether these numbers mean anything worthwhile to a fantasy owner. Doing a quick correlation analysis, we can see that wOBA is highly correlated with ERA (R^2 value of 0.77) so all this number crunching has real fantasy applications:

wOBA - 2019
Enjoy the list and please click on the baseball card to visit our partner amazon.com to explore additional information on each player.

Hot Rods

Name wOBA xwOBA Difference
Jose Quintana 0.380 0.311 0.069
Eduardo Rodriguez 0.380 0.315 0.065
Freddy Peralta 0.340 0.289 0.051
Lance Lynn 0.298 0.268 0.030
MLB Average 0.317 0.317 0.000

Jose Quintana (CHC, LHP)

The Cubs pitcher has been a disappointment since arriving in the Windy City and continues to be unable to find any consistent footing. Although his last start – where he struck out 11 Pirates over seven shutout innings– was encouraging, is it a sign of a turnaround? After all, his composite season stats (including this dominating start) are still a gaudy 1.71 WHIP and 5.14 ERA (or 1.60 WHIP and 7.20 ERA if you don’t count his early season relief appearance). Well, owners can breathe a sigh of hope as his Stat Cast data suggests that his xwOBA is better than league average (and his SIERA is a trim 3.27). Look for better days ahead.

Eduardo Rodriguez (Bos, LHP)

Another southpaw shows up next on this list. Although all of the Red Sox have been struggling, the 26-year-old hurler has been suffering the same fate too, spinning an ugly 1.70 WHIP and 7.98 ERA. Luckily for the Beantown faithful, this seems to be “merely” bad luck as his expected wOBA against is actually that of a league average pitcher. In other words, expect some regression back to an ERA of 4.20 (which is what his pre-season projections were calling for and the performance floor that owners were expecting on draft day). It might be cold comfort that he “should” be pitching at his ‘floor’ – but right now, Boston fans would do well to take any signs of optimism.

Freddy Peralta (Mil, RHP)

The young Brewer hurler is a model of inconsistency so far this year as his 3 starts have been a meaty gem of a game (11 Ks over 8 shutout innings) surrounded by two blow-ups ‘buns’. In aggregate though, his xwOBA against is actually better than league average and his season’s 6.91 ERA really should be closer to his 3.64 SIERA. He may be a rollercoaster ride in redrafts this year but I’m still buying in dynasty.

Lance Lynn (Tex, RHP)

The former Cardinal (and Twins) pitcher has been pitching well thus far in Arlington (after a terrible debut), most recently striking out nine Diamondbacks in his last outing. Despite his gaudy 4.78 ERA, his FIP is 3.15 (SIERA of 3.69) and his WHIP is a tidy 1.18. And although his wOBA is already better than league average at 0.298, his expected wOBA is actually even better at 0.268. Doing a further deep dive on his individual pitches shows that all five of them (his 4-seam, his 2-seam, his cutter, his curve, and his changeup) all have xwOBA’s against that are better than league average. In other words, it’s likely not a pitch sequence issue that needs to be solved – but rather literally just bad luck/defense. I just picked him up in two leagues – so we’ll see if the analysis bears out.


Name wOBA xwOBA Difference
MLB Average 0.317 0.317 0.000
Shane Bieber 0.180 0.319 -0.139
Matt Shoemaker 0.223 0.329 -0.106
Jake Arrieta 0.272 0.366 -0.094
Aaron Sanchez 0.279 0.363 -0.084

Shane Bieber (CLE, RHP)

So far for Cleveland, the young starter has posted a 0.62 WHIP and 1.38 ERA. You know that regression is in the cards as these numbers are unsustainable – and the StatCast data supports this, indicating that his ERA really should be league average (ie around 4.20). Ride it while you can.

Matt Shoemaker (TOR, RHP) and Aaron Sanchez (TOR, RHP)

Although the Jays’ season has been merely biding time until the Vlad call-up, in the early going, the starting pitchers have pleasantly surprised with a 2.71 ERA, 3rd best in the league. Unfortunately, that has been due in large part to overachievement from Shoemaker and Sanchez. They have two of the largest discrepancies between actual wOBA and expected wOBA. Most fantasy owners are savvy enough to know that they should be holding onto Shoemaker while the good times last so they’re unlikely to be surprised when he falls back to Earth – but those hoping that Aaron Sanchez may be indicating that he is poised to repeat his ‘blistering’ 2016 campaign when he led the league in ERA, will likely be disappointed. His ERA is 1.69 but his SIERA is 4.89…and that is more in line with how he should be performing.

Jake Arrieta (PHI, RHP)

The former Cy Young award winner shows up on the list boasting a 1.15 WHIP and 2.25 ERA thus far in the 2019 season. But looking under the hood, we see nothing but red flags. His SIERA is 5.41, his xwOBA is 0.7 standard deviations worse than league average and he’s not missing any bats either (5.6% Swinging Strike rate). He may still get wins on a contending Philadelphia club, but don’t expect much else. Another negative indication is that all of his pitches (sinker, changeup, curveball, and slider) have xwOBA’s significantly worse than the league average.

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