How the D-backs Were Able to Revamp Their Bullpen Midseason

Once the fatal flaw for many years, the bullpen has become a strength in the Diamondbacks' postseason run.

In postseason baseball, games and series come down to the bullpen. For the past five years, it has been a sore spot for the Arizona Diamondbacks. Between a revolving door of closers and a lack of certainty in roles, many a reliever struggled in the desert. In order for the 2023 squad to be able to compete for a postseason spot, they needed a bullpen that was at least serviceable and could close out late leads. 

For much of the 2023 season, they tried to follow the Tampa Bay model, relying on matchups to predicate the closer role, but that did not work. Veterans Andrew Chafin, Scott McGough, and Miguel Castro struggled in the 9th inning, leaving the team desperate for solutions. They went out and paid a premium to land Paul Sewald, giving up two players off their active roster and one of their top infield prospects, to stabilize the closer's job. 

"When we acquired Paul, we had talked about not having a closer for a couple of years now," said the recently extended general manager Mike Hazen. "That was my fault. We tried to piece it together in various ways. When we did acquire that closer, when we got him, I think what it did by pushing everybody a little bit forward was settled everybody into roles and allowed for stability to happen around that.

While Sewald himself hasn't been lights out, with a 1.47 WHIP and 5.1 walks per nine innings in 20 appearances with Arizona, he has converted 13 of 15 save opportunities (87%) in the regular season followed up by a pair of three-run saves in Milwaukee. With the closer role finally situated, the next step was finding arms that could get big outs from anywhere between the 6th and 8th inning. The pitchers who stepped up into those roles ended up being Kevin Ginkel, Ryan Thompson, and Andrew Saalfrank. Those three have empowered manager Torey Lovullo to be more proactive in his bullpen usage.

"When you talk about feeling empowered, I think that's a very powerful statement, but it's real," said Lovullo. "It's part of what makes your team good when you have a lot of options that aren't just throw-away options; they're legitimate options that will help you win a game.

Ginkel was the first key reliever to step up in the season, now Lovullo's most trusted setup man. In medium and high leverage situations this season, the 29-year-old right-hander has held opposing hitters to a .191/.267/.270 slash with a strikeout rate above 30%. With Sewald handling the 9th, Ginkel then became the next reliever on the pecking order with the 8th inning along with some occasional matchups before. Thompson and Saalfrank have become key matchup arms, as evidenced by their usage in the Milwaukee series. Both pitchers inherited bases loaded, one-out jams and hung up a zero in what proved to end Milwaukee's momentum for that particular game.

"I'm still a young manager when it comes to playoff baseball experience," said Lovullo. "But through a lot of the conversations I've had over the years with managers that have been in this arena and watching games -- and I try to tell you guys this -- it's stopping the momentum."

Having those four arms trusted to handle the big situations, has created a cascading effect that's allowed the other pitchers to succeed in lower-leverage roles. Castro and Joe Mantiply have pitched well as low-to-medium leverage arms in the middle innings, combining to allow just one earned run in September in 22 2/3 innings and 1 1/3 scoreless innings in Game 1 vs. the Brewers. While the big four of Sewald, Ginkel, Thompson, and Saalfrank have rightfully received the praise coming their way, the four outs that Mantiply and Castro got on a night the bullpen needed 19 should not go unnoticed.

Even with a bullpen that's clicking, the D-backs will face a tough challenge against one of baseball's best teams year in and out in the Dodgers. Having a reliable bullpen will be one of the big keys for them to pull off the sixth-largest upset in MLB postseason history based on the difference in winning percentage (98 points).