Best relief pitchers of all time: The best relievers in MLB history

Though the position has been expanded heavily recently, a list of the best relief pitchers in MLB history would include pitchers from multiple decades back. Who makes our list?

As part of a series we will cover here at Call to the Pen on MLB history, today we will look at the best relief pitchers of all time.

We will cover all of MLB history, not just the first 100 years or the last 50 years, and this is not a consensus of all Call to the Pen authors and editors, but the opinion of the author of that list. This is a great list to debate and discuss!

Before we move to the top 20, let’s look at one current player who has a chance to break into this top 20 list!

Josh Hader, LHP

Career Stats: 62 G, 7 SV, 88 1/3 IP, 1.73 ERA, 0.88 WHIP, 11.24 BB%, 43.79 K%
A local guy from the Baltimore area, Hader was elated to be picked by his local squad in the 19th round in the 2012 draft, but after a pair of trades that first took him to Houston and then to Milwaukee, Hader has emerged with a chance to be the most dominant reliever of his era.

While other pitchers have had dominant runs over a short time, none have had dominance near what Hader has been doing so far. Hader’s strikeout rate really should be put in some level of perspective.

Thus far in 2018, Hader has thrown 40 2/3 innings, with a 16/80 BB/K ratio. That equates to a 53.33% strikeout rate. In the history of the game, two pitchers have ever recorded over a 50% strikeout rate in a season with more than 40 innings pitched. Hader leads all by almost a full percentage point with the highest strikeout rate ever seen in the history of the game with at least 40 innings thrown.

That isn’t selection bias. If you lower the standards to 35 innings, he’s still the top of the list. Same with 30 innings, 25 innings, 20 innings, 15 innings, and even 10 innings. You have to set the minimum to 5 innings pitched in a season to find any pitcher in the history of the game who has had a strikeout rate higher than what Hader is doing in 2018 – and Hader’s still #2!

The temptation will be heavy for the Brewers to put Hader into the rotation with his 3-pitch mix, but he’s so dominant in his current role that it will be hard to move him.

While we wait to see if Hader will eventually join the best relief pitchers of all time, let’s take a look at the guys who do make the list…

Next: 25. A 32nd round find