Yesterday, I listed and discussed the hitters with at least 200 PA who have most underperformed their xwOBA marks. Today, let’s now flip to the overperformers, those who have posted wOBA marks most above their xwOBA marks.
It’s been nearly two months since I reviewed xwOBA and listed and discussed both the underperformers and overperformers. So let’s get back to it as we near the halfway point in the season. Obviously, xwOBA isn’t perfect. No expected metrics are and they never will be. However, it does a better job of predicting future wOBA than wOBA itself, even though it’s not even built as a predictive stat (it’s backward looking). So with that in mind, let’s investigate the hitters who have most underperformed their xwOBA marks so far.
A former Mets farmhand who amassed 68 innings in the Majors before pitching for a season in KBO (Korea) last season, Chris Flexen 플렉센 signed with the Mariners this past offseason as a real mystery man. Incredibly, he actually entered the 2021 season with more walks allowed than strikeouts during his short MLB career, but a 28% strikeout rate versus just a 6.4% walk rate in Korea suggested that maybe something had changed. So suddenly he was an interesting flyer in fantasy leagues with the possibility he learned something overseas that would translate back to the Majors. That certainly didn’t happen over his first eight starts, but things might be clicking now, as we’ll see over his last five starts.
Yesterday, I reviewed the starting pitchers leading the league in SIERA over the last 30 days. Now let’s flip to the other end — those starting pitchers who have posted the worst SIERA marks in the league over the last 30 days. Is a decline in velocity to blame? Sudden control issues? Let’s find out.
Pitchers can change rapidly. Whether it’s changing their mix pitch, gaining or losing velocity, adjusting their mechanics, or something else, a pitcher we see today isn’t necessarily the same version we were expected during draft season. So it’s important to always monitor their underlying skills to see if the results suggest a new pitcher has arrived, whether better or worse. With that in mind, let’s dive into the last 30 day SIERA leaders. Are there any surprises among the crowd?
Today we continue our look into middle reliever targets (AL is here), switching over to the National League. As a reminder, here are my filters:
>=30% strikeout rate
>=20% K%-BB%
>=15% SwStk%
I also required a minimum of 20 innings pitched.
Injury or poor performance from your starting pitchers often times leads to a decision — do you want to replace that starting pitcher with a starter from the free agent pool who could potentially harm your ratios, or pluck a strong middle reliever who could stabilize those ratios, but might limit your win and strikeout totals? There’s no correct answer. However, if you do decide on the latter strategy, let’s review some of the names that should be at the top of your shopping list.
Yesterday, I perused the Triple-A SwStk% leaderboard and listed and discussed the AL starting pitchers who were at the top. Now let’s flip over to the NL, which unfortunately is a far less exciting group.
Over the last two days, I have listed and discussed the Triple-A starting pitchers who appear atop the strikeout rate leaderboards, in both the AL and the NL. You may have noticed I also talked a lot about the pitcher’s SwStk% and how it matched up with his strikeout rate. If there’s a metric I like to follow even more than a pitcher’s minor league strikeout rate, it’s possibly SwStk%. Though this is just anecdotal, it feels like if a pitcher has posted a high strikeout rate, but just a mediocre SwStk% in the minors before his MLB promotion, he more often disappoints in strikeout rate in the Majors, suggesting his SwStk% was the metric that translates better, rather than strikeout rate. With that in mind, let’s check out the AL SwStk% leaders at Triple-A that have pitched the majority of their innings in a starting role.
Yesterday, I listed and discussed the Triple-A starting pitchers atop the strikeout rate leaderboard. Now let’s flip to the NL.
