Shelby Miller’s Comeback: From Bust to D-backs Bullpen Star

Shelby Miller's second stint with the Arizona Diamondbacks could not get off to a much better start. The right-hander has not allowed an earned run in 13.2 innings and has quickly emerged as one of the top arms in the bullpen.

"My first time around here wasn't that great, but getting to come back and succeed so far and just continue that success hopefully, and then it's just amazing to be back and be a Diamondback and be in Arizona for sure," Miller told DbacksTV reporter Jody Jackson after his successful save opportunity on Thursday.

Prior to this season, the lasting memory of Miller for Diamondbacks fans was a pitcher whom the team paid a premium for and failed to live up to the billing. Arizona had traded a significant prospect haul, including former 2015 top pick Dansby Swanson, to the Braves to acquire the All-Star right-hander. In a twist of fate, his first outing in his return to the Diamondbacks was facing Swanson for the first time nearly 10 years after the trade.

After Miller left Arizona following the 2018 season, his career was at a crossroads. He had struggled to find his footing in the major leagues for the next four seasons, but found something toward the end of the 2022 season. Since then, he's been on an upward trajectory for his career and has reinvented himself as a solid right-handed reliever.

Despite his success with the Dodgers and relatively solid underlying metrics on Statcast in his year with the Tigers, Miller had to sign a minor league pact with the Diamondbacks in February. From the start of spring, he's been lights out and made the club on his own merit. In the first month of the season, he's proven to be a reliable arm and is getting higher leverage situations.

In his last six outings, Miller's average leverage index on Baseball Reference averages 2.80. For context, anything higher than 1.0 is considered high-pressure situations. That's come out of necessity as both the team's high-leverage relievers, A.J. Puk and Justin Martinez, are battling injuries. With both of them on the shelf, Miller will be tasked with getting a lot of those outs for the bullpen.

It will be interesting to see how manager Torey Lovullo divvies up the roles in the bullpen as it's currently constructed. Based on results and underlying performances, it would make sense to ask Miller to get the biggest outs of the game. Whether that's pitching the ninth or facing the heart of an opposing lineup in the eighth, that should be his role.

The 34-year-old doesn't have a lot of experience pitching in the ninth inning. He has four career saves, the latest coming in Thursday's series-clinching win over the New York Mets. In that series, he pitched a scoreless eighth in the second game, then pitched a tidy ninth in just eight pitches in the finale.

"Big innings, there's more adrenaline than when you're behind. So, you know, like seventh, eighth ahead, that's some adrenaline, but I think closing games is probably the most for sure."

Diving into what has made Miller successful this season, he carries a three-pitch mix. It starts with a very lively fastball, averaging 94.5 MPH with above-average horizontal and vertical break. Because of the sheer movement numbers on the pitch, and his ability to fill up the zone with it, batters are just hitting .143 and slugging .143 against his fastball this season. In just a short stretch of the season, it has generated a +4 run value.

Having a plus fastball isn't the only reason that Miller has been successful; he can also throw some quality secondary stuff. The splitter has been a key pitch in his revival as a reliever. He developed it in his one year with the Dodgers in 2023, and it's become his go-to secondary offering, especially against lefties.

Over the last three years, the splitter has had a mixed track record. In 2023, it had a +2 run value, then -3 in 2024. Looking deeper into his 2024 numbers, the results did not match the quality of contact as his xBA (.227) and xSLG (.385) were better than the actual results of a .239 average and .457 slugging. That likely factored in the Diamondbacks' decision to sign him, despite a cold market for his services in terms of major league contracts.

In 2025, the pitch has taken off to new levels and has become a real weapon for Miller to put away hitters with. The splitter has already generated a +3 run value, as batters are hitless against the pitch with a 37.0% whiff rate. Factoring in that hitters have to expect an explosive mid-90s fastball, the ability to land both pitches puts hitters in a bind. It's no surprise the two pitches have combined for a +7 run value to begin the season.

Due to the quality stuff he holds, plus the ability to command it, Miller has one of the best chase rates in baseball at 41.8%. That's led to either whiffs or soft contact, as his 31.6% whiff rate sits in the 82nd percentile and average exit velocity of just 84.8 MPH. The combination of swing-and-miss and weak contact is ideal to have in the back of the bullpen.

While he isn't likely to sustain a 0.00 ERA, his 1.96 FIP and 2.23 xERA are both bullish on his run prevention ability. If he continues this, Miller will end up being the high-leverage bullpen arm the Diamondbacks have needed all season. At this point, it's incumbent that Lovullo use his best reliever available for the biggest situations of the ballgame, regardless of what inning it is.

If Miller emerges as a key late-inning arm and the Diamondbacks make a deep postseason run, it will complete quite the redemption arc in the right-hander's career. That will be the lasting memory for fans, not the failed starter arc from one of the franchise's most infamous trades from 2016-2018.

Shelby Miller’s Comeback: From Bust to D-backs Bullpen Star

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