Baseball’s Top Relievers Are Really Good

Tuesday night, I watched Ryan Helsley face the middle of the Brewers order in the bottom of the eighth inning. It went roughly how you’d expect – strikeout, groundout, strikeout. He came back out for the ninth, and after an inning-opening walk, closed out the frame with another two strikeouts and a groundout. It didn’t feel surprising; that’s just what great relievers do at the end of games.

That wasn’t always the case. The game has changed over the years. Relievers are pitching fewer innings per appearance, and doing so in better-defined roles. Strikeouts are up everywhere. Velocity is up everywhere. Individual reliever workloads are down, which means higher effort in a given appearance despite bullpens covering more aggregate innings. I’m not trying to say that the current crop of relievers doesn’t have structural tailwinds helping them excel. But seriously – top relievers now are so good.

Look at the top of this year’s WAR leaderboard for relievers – either RA9-WAR or FIP-based WAR will do – and you’ll see a veritable wall of strikeouts. Edwin Díaz, Devin Williams, A.J. Minter, Helsley, and Andrés Muñoz are all in the top 10 and all run preposterous strikeout rates. They’re good in an in-your-face way. Since I’ve watched baseball, dominant late-inning relievers have succeeded by striking batters out, but that trend has accelerated in the past decade or so. Here, take a look at the strikeout rate of the 10 top relievers in baseball, as determined by fWAR, every year since integration:

For the past five years or so, the most valuable relievers have been striking out more than a third of their opponents. Sure, strikeouts have gone up across all of baseball, not just for a handful of relievers. That handful of relievers, though, is outstripping the league as a whole by more than ever:

Relievers used to be just regular pitchers in the 1940s and ’50s. By the ’70s and ’80s, a new class of dominant late-inning pitchers arose. But even in 1983, when Goose Gossage compiled a 2.27 ERA over 87.1 innings of work with the Yankees, top relievers weren’t that much better than the league as a whole when it came to strikeouts. Gossage was a standout, fanning 24.5% of his opponents, but the top 10 relievers in aggregate struck out only 18.7% of opposing batters, while pitchers overall checked in at 13.5%. Maybe a few top relievers were scary, but the crop of very good late-inning guys mostly looked like a slightly improved version of pitchers as a whole.

By the early 2000s, top relievers had established themselves as standouts in the field of strikeouts, running strikeout rates roughly 10 percentage points higher than pitchers as a whole. Today, that edge has pushed out into the 12 to 15 point range. Combine that excellence with the increase in strikeouts across baseball, and top relievers now are striking out batters at a clip previously unseen in history.

A silly way of thinking about it: if you aggregated this year’s top 10 relievers into a single pitching line, that aggregate pitcher would have a strikeout rate higher than all but two reliever seasons from the 1980s (1987 Tom Henke and ’89 Rob Dibble). It would be eighth in the 1990s, or 16th in the 2000s. The average strikeout dominance of the best closers in baseball these days looks a lot like a standout season from decades past.

If that’s all there was to it, I’m not sure I would be writing this article. Watching baseball today, it’s clear that strikeouts are on the rise everywhere. But these top guys aren’t just striking out a pile of batters. They’re better than any previous class of top relievers. The best bullpen arms in the game are neutralizing opposing lineups like never before, and I’ve got the charts to prove it.

Let’s get some quick details in before I blow your mind with pictures. I took every season in baseball where a pitcher threw at least 50 innings, and where more than half of their appearances were in relief. This isn’t perfect, but it does a good job stripping out swingmen and pitchers who made a few early-season relief appearances before becoming starters. Spencer Strider doesn’t appear on this year’s list, for example. From there, I ranked each season in a variety of categories. I focused on the top 10 relievers by category in each year because that seems like a good definition of the elite guys, the ones who feel like sure things relative to the rest of the league.

Across all pitchers, ERA has oscillated up and down over the past 70 years. It’s in the same place now as it was in the late 1950s, the late ’70s, and the early ’90s. Meanwhile, the ERA of the 10 best relievers in baseball, as measured by fWAR, just keeps going down:

If 2022 ended today, it would feature the second-lowest ERA by the top relievers in baseball that we’ve ever seen, a rounding error behind the 1.93 mark from ’06. And this isn’t some fluke of using FIP, either. If you simply take the average ERA of the 10 relievers with the lowest ERAs, this year is third in history, behind only 2013 and ’14, the two lowest-offense years of the 21st century.

Maybe you don’t like to think of relievers in terms of fWAR. Fair enough! Helsley, who I think is a great example of this class of ultra-closer, isn’t one of the top five relievers in baseball by fWAR. Reynaldo López, more nice arm than fear-inspiring closer, is roughly even with Helsley. He has a 2.84 ERA and no saves, which isn’t exactly what I’m looking for. When I’m talking about the top relievers in baseball as a class, I want the guy you’d be terrified to see come in, the one with trumpet fanfare and flashing lights. Let’s redo these charts using RA9-WAR, which should get the guys we want: relievers who pitch a ton of high-leverage innings and don’t allow any runs.

Here’s the strikeout rate chart for top relievers by RA9-WAR over the years:

It’s more of the same: the end-game bosses are vaporizing opposing hitters like never before. If you’re into RA9-WAR, in fact, this season’s crop of top relievers has the lowest ERA ever:

Ever since top relievers have started striking out such gobsmacking rates of opposing batters, their run prevention numbers have fallen in line. The top 10 relievers in baseball by RA9-WAR have posted an aggregate ERA below 2.00 in 17 of the last 20 seasons. In the 20 seasons before that, they did it only four times. In the 20 seasons before that, a span that includes 1968, they did it exactly once, and with a 1.99 ERA at that. Some of that is because there are more relievers in baseball now, but most of it is because the guys at the back of the bullpen are better at what they do than ever before.

It’s tempting to think that baseball is static across eras. Run scoring is roughly the same, so why shouldn’t the various components of it be the same? But that’s not true. The very best late-inning relievers in the game are better, by a huge margin, than their predecessors. They train for this. They make hitters look foolish like no relievers before them. They’re a walking proof of concept for the whiff-centric theory of pitching development that every team in baseball now teaches: strike out this many batters, and your ERA will dwindle.

This isn’t a phase. It’s not some one-year thing, though the best relievers of 2022 look like a pretty good crop on a relative basis. It’s just the way baseball is going. Teams are trying harder to develop great relievers, and relievers are getting better at turning raw swing-and-miss potential into in-game filth. We’re living in the era of closer dominance. Don’t let the fact that so many relievers are having good seasons blind you to how impressive each feat is. The best inning-for-inning relief seasons are disproportionately happening right now, and I see no reason to think that will stop any time soon.