Baseball’s Top Relievers Are Really Good

© Jeff Curry-USA TODAY Sports

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.

Ben is a writer at FanGraphs. He can be found on Twitter @_Ben_Clemens.

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1 year ago

Edwin Diaz in this season is more or less the best reliever performance since any one of Craig Kimbrel’s best seasons (you can pick any of them and it still works). Diaz basically punching out 2 batters an inning, which is insane on a whole bunch of levels, but it’s even crazier because he’s not walking a lot of guys either. With apologies to Kenley Jansen, Josh Hader, Aroldis Chapman, and Dellin Betances–probably his closest competition in the 21st century–what he’s doing right now is just impossibly good.

It’s wild because between Williams, Helsley, and Munoz you’ve got three guys who themselves are shredding batters and not even giving them a chance, with Clase channeling his best Zack Britton impersonation getting balls on the ground roughly 2/3rds of the time while still sporting a gaudy K:BB ratio. There are 62 (!!!) qualified relievers who are striking out more than 10 K per 9 innings. So it’s not like there’s not competition. And here Edwin Diaz is, posting the second highest K rate of the 21st century for a reliever. What a monster.

1 year ago
Reply to  sadtrombone

Funny you mentioned Kimbrel. A few years ago, I made up a made-up stat called “Kimbrels”, which counts the number of games where a pitcher had a negative FIP. You pretty much have to have a 2K, 0 BB inning outing or better to get a Kimbrel. Looking at Diaz’s game scores, so far this year he has had 30 Kimbrels, which is incredible.

Moving to better-known stats, Diaz right now is one of just 4 pitchers to have pitch 50+ innings in a season with a FIP below 1.00:

2012 Kimbrel: 0.78
2003 Gagne: 0.86
2014 Chapman:0.89
2022 Diaz: 0.90

Mr. Redlegsmember
1 year ago
Reply to  tz

Would love to see the “Kimbrel” leaders for 2022.

1 year ago
Reply to  Mr. Redlegs

Here’s an unofficial 2022 top 5 (I have to do these by hand, so I might have missed someone):

2022 Kimbrel Leaderboard

  1. 30 Edwin Diaz
  2. 22 Devin Williams
  3. 21 Joe Jimenez (tie)
  4. 21 A. J. Minter (tie)
  5. 20 Caleb Thielbar
1 year ago
Reply to  tz

Using the Splits leaderboard, looks like you nailed the top five 🙂

30 Edwin Diaz
22 Devin Williams
21 A.J. Minter
21 Joe Jimenez
20 Caleb Thielbar
19 Alex Vesia
19 Andres Munoz
19 Emmanuel Clase
19 Jose Alvarado
19 Josh Hader
19 Trevor Stephan
18 Adam Ottavino
18 Erik Swanson
18 Felix Bautista
18 Jason Adam
18 Rafael Montero

Kenley Jansen only has 15 Kenleys…

1 year ago
Reply to  rosen380

…and now for “Platinum Kenleys” (min 5 IP):
3 Shohei Ohtani
3 Zac Gallen
2 Spencer Strider
2 Brandon Woodruff
2 Carlos Rodon
2 Clayton Kershaw
2 Eric Lauer
2 Justin Verlander
2 Max Scherzer
…14 more with 1.

1 year ago
Reply to  rosen380

Fun Ohtani Fact #8675310: if you first start of this season, which only went 4 2/3 dominant innings, Ohtani has 4 of these gems as a starter this year. This is as many as Pedro Martinez has back in 1999, when he set the record for FIP- by a starter with 31 (1.39 FIP), as well as Corbin Burnes last season.

1 year ago
Reply to  rosen380

Did Ty Blach just throw a Kimbrel against the Giants last Wednesday in a near immaculate inning?

Gary Palmersonmember
1 year ago
Reply to  tz

I made a stat called a Kimbrel years back which is a perfect 3K save. My friend refuses to acknowledge it and calls it a Lidge, but the all time leaderboard is on my side