Despite recent hurdles, Joe Mantiply is having one of the best first halves ever by a Diamondbacks reliever

You’ve probably heard it said by now: The Diamondbacks had to have someone in the All-Star game.

Disrespectful? Sure. Wrong? Well, not really. The D-backs did need a representative, and that someone is left-handed reliever Joe Mantiply. ​​

While many baseball fans view his All-Star selection as nothing more than an obligatory formality, Mantiply’s first half has been remarkable — particularly for a franchise that has been riddled with bullpen problems since its inception.

The timing of this piece is unfortunate, given that Mantiply’s ERA has more than doubled in the past 10 days. Still, entering Tuesday’s game in San Francisco, Mantiply had a 2.08 ERA, 0.95 WHIP, 25.0 percent walk rate and 1.5 percent walk rate over 34 ⅔ innings. At first glance, it already feels like few Diamondbacks have ever reached that level.

To better understand how Mantiply’s first half stacks up with others in Diamondbacks history, fWAR and ERA- (read as “ERA minus”) come in handy. The former is not a particularly great stat for relievers, but it is a helpful starting point to narrow down the field of possibilities. ERA- helps account for the fact that posting a 2.50 ERA in 2002 is not the same as doing so in 2022. 

ERA- is essentially an adjusted version of ERA where league-average is set to 100 and lower is better. An ERA- of 80 indicates that a pitcher was 20 percent better than average at run prevention. Another helpful factor here is that ERA- is park-adjusted, meaning it accounts for, say, one guy pitching a lot in Coors Field versus another guy who pitched more frequently in San Diego.

Using fWAR and ERA- in conjunction, here are the top 20 first halves by relievers in Diamondbacks history, ranked by ERA-. (I was unable to get FanGraphs to give me fWAR numbers for specific portions of a season prior to 2002, hence why Greg Swindell and Byung-Hyun Kim’s are missing.)

Mantiply ranks sixth on the list in ERA-, trailing only 2017 Archie Bradley, 2007 Tony Peña, 2000 Greg Swindell and a pair of seasons from Andrew Chafin.

Granted, ERA is not the end-all-be-all of pitching stats, particularly for relievers. Since ERA- is based on ERA, it carries the same flaws. To control for external factors that inevitably distort ERA and ERA-, FIP is a helpful metric that uses the same scale as ERA but attempts to capture the aspects of the game a pitcher controls more directly: strikeouts, walks, hit batters and home runs. 

Mantiply’s FIP in 2022 is 2.33, which is close to his 2.08 ERA. The relatively small disparity between those numbers suggests his success this season isn’t a fluke. That is not true for all pitchers on the list above. To narrow down further, we can remove pitchers with a FIP of 3.00 or higher. Doing so nearly cuts the list in half:

At this point, ranking the remaining names gets difficult. Archie Bradley has a compelling case for the top slot, and not just because of his 24 ERA-. His ERA and WHIP are both the lowest in the group, and he also logged a relatively high volume of innings at 41.

Speaking of innings, Byung-Hyun Kim threw 58.1 of them in the first half of his 2001 season and another 51 in the first half of 2002. Numbers like those for a closer are unheard of in the modern game. For comparison, only a handful of closers have even reached 40 innings so far in 2022. Maybe Kim’s sheer workload is enough to put his 2002 first half over the top?

Andrew Chafin’s 2017 and 2018 first halves stack up well against Mantiply’s first half in 2022, but Chafin also faced a higher proportion of left-handed hitters than Mantiply. Of course, a lot of that has to do with the fact that the three-batter minimum rule was not instituted until 2020. Mantiply has been forced to face more righties, and he has excelled in doing so.

No matter the order you prefer, Mantiply is near the top. He has the fourth-lowest ERA- of the group, the second-lowest WHIP and the second-lowest FIP. His strikeout rate is not as high as some of the others, but his walk rate is by far the lowest at 1.5 percent.

For a franchise that has struggled to find reliable relievers, Mantiply’s emergence as one of baseball’s best in 2022 is a welcome sight. It also begs the question: Can he do it again in the second half?

Follow Jesse Friedman on Twitter

Top photo: Eric Hartline/USA TODAY Sports

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