A slump-proof, lockdown bullpen doesn’t just win games. It can effectively end them before they’re over. But relievers are weird. Even when they’re not pooping their pants, they’re probably the most volatile players in all of baseball. They seem to represent only the foremost moment in any given season, making trying to project which ones will be good largely a fool’s errand.
But there is a tool that can help, maybe: SIERA. That’s Skill-Interactive ERA. It’s an ERA estimator like FIP or xFIP, but it’s better because it accounts for more of the noise that can result from batted balls. It also has a stronger correlation to predicting a pitcher’s future ERA.
It’s important to acknowledge that it isn’t an ERA projector, but can inform us of the quality of the skills a pitcher has demonstrated most recently. And now, as the season heats up, and as potential playoff teams show more urgency, and we’re in the foremost moment the season has to offer, we can use SIERA to see which of baseball’s oddest bunch could offer big benefits in the second half. Let’s dig in.
Juan Nicasio currently has a SIERA of 2.49. His ERA is a flat 6.00 through 34 appearances. Because SIERA is best used as a starting point for evaluating a player, the disparity between his results versus how he’s actually pitched pushes us to look further. One thing that jumps out is his strand rate, which stands at a homely 53.3%. That’s 20% worse than league average for relievers. It’s probably fueled by a .396 BABIP which is a whole hundred points worse than league average, and this is all happening while he’s striking out more and walking less batters than he ever has.
The thing about Nicasio isn’t any of those wonky stats, though. It’s that it’s hard to see him not getting better while playing on a team that’s been thriving in one-run games all season. The Mariners may effectively gain a lockdown arm for their bullpen as the ledger balances for him, and they’ve already had a top ten group by fWAR. What they’re doing is unprecedented and Nicasio is another reason it could keep happening.
Will Harris would likely elicit a shrug from anyone who peered at his 4.15 ERA. His FIP and xFIP are both sub-3.00, though, and his SIERA is an even tinier 2.40. Including him here might be considered cheating in two ways: he’s appeared in ten games over the last month with an ERA of 2.70, and he’s an Astro.
He was victimized by home runs earlier in the year and has been better at keeping the ball in the park, having allowed only one dinger over the last 30 days. It helps that he’s striking out a career high, too, with a reworked curveball that’s tighter and sharper than ever. Remarkably, he might only be the third-best Astros reliever behind Collin McHugh and Brad Peacock. Maybe it’s not cheating so much as it is just unfair that the Astros could get even better with a guy they’re already trotting out there.
And then there’s a pair of Phillies, Hector Neris and Tommy Hunter. Neris has become much maligned and was even sent to the minors to figure himself out. He’s given up a homer on nearly every third flyball allowed, which is bonkers. His fastballs have flattened out, which probably plays into his splitter playing down, too. While his 6.90 ERA is woof-worthy, his 2.95 SIERA is pretty nice and tells us his fastballs being worse shouldn’t make him this bad.
Phillies general manager Matt Klentak caught some flak on talk radio for recently saying that Tommy Hunter’s 2018 has actually been one of his best. His ERA is approaching 5.00 but his SIERA sits at 2.87, so maybe Klentak’s statement gives us a glimpse into the team’s beefed up sabermetric approach. Hunter has fallen victim to similar issues as the others above — high BABIP causing a lower strand rate.
The thing about Hunter (25.1) and Neris (30) is they’ve accounted for 55.1 innings out of the Philadelphia bullpen. Positive regression for them could be critical for the team, as others like Edubray Ramos and Victor Arano are slightly outperforming their peripherals so far. They’re on pace for 88 wins, and every inning is going to be important for them in the second half as the team pushes for the playoffs for the first time since 2011.
Looking at a pitcher’s SIERA gives us a stronger sense of their most recent performance. It can also give us a sound starting point for where else to look to understand how the moment has treated them. Beyond that, it can also help us zoom out and examine a pitcher’s potential impact on their team while we move onward to October, no matter how weird they are or have been.
Data from FanGraphs. Feature image from Elaine Thompson/AP.