On paper, few teams had more productive off-seasons than the Diamondbacks.

They brought back outfielder Lourdes Gurriel Jr., who has been one of their key contributors so far this season. They upgraded at third base by trading for Eugenio Suárez. They further bolstered their lineup by signing Joc Pederson and Randal Grichuk. They added a pair of well-established lefties to their starting rotation in Eduardo Rodriguez and Jordan Montgomery.

According to Spotrac, the Diamondbacks spent roughly $202 million on off-season contracts, the fifth-highest total in baseball. In the process, they set a franchise record in payroll, shattering their previous record by more than $25 million. They drew widespread praise for their investments.

In spite of all the additions they made, however, the Diamondbacks left one aspect of their team essentially untouched: the bullpen. And, while there are many reasons for their lackluster 11-13 start to the 2024 season, the bullpen has arguably been the biggest one.

The Diamondbacks’ loss to the St. Louis Cardinals on Monday is the latest example.

After working out of a jam in the sixth inning to preserve a 3-2 Diamondbacks lead, right-handed reliever Scott McGough, who posted a 4.73 ERA last year in 70.1 innings, served up a game-tying home run to slugger Paul Goldschmidt on a middle-middle fastball in the seventh.

With the game still tied in the bottom of the ninth, left-hander Kyle Nelson was brought on to face Cardinals lefty Nolan Gorman with a runner at first and one out. Gorman smoked the first pitch he saw 425 feet into the right-field bleachers for a walk-off homer.

It was the ninth game this season that the Diamondbacks lost despite having a lead. They have led in 20 of their 24 games, but only have 11 wins to show for it.

Of course, the Diamondbacks’ bullpen was not the only reason for Monday’s loss, nor the sole reason for many of the team’s comeback losses this season. The Diamondbacks’ defense has unraveled in several pivotal moments. Their hitters have a .416 OPS in high-leverage situations, magnifying any lack of execution in other areas.

It also bears mentioning that Diamondbacks closer Paul Sewald has been sidelined all year due to an oblique strain. Sewald is expected to start a rehab assignment with Triple-A Reno on Tuesday and could be back with the team soon. He played a crucial role in helping the bullpen turn things around last year.

Nonetheless, the fact that the bullpen has struggled to this degree at least raises the question: Will the Diamondbacks regret their decision to run it back with the same bullpen they had last year?

Diamondbacks’ Bullpen performance to date

On the surface, the Diamondbacks’ bullpen has actually been alright in 2024. The unit has a 4.18 ERA this year, which ranks 18th in baseball; not good, but not terrible, either.

Of course, not all innings are equally important. A scoreless inning in a tie game is much more valuable than a scoreless inning in a blowout. So far, Diamondbacks relievers have been much more effective in moments of lesser significance.

In 72 innings of work in low- or medium-leverage situations (as defined by Fangraphs), Diamondbacks relievers have held opponents to a .234/.290/.370 slash line.

In 16 1/3 high-leverage innings, on the other hand, D-backs relievers have gotten hammered to the tune of a .369/.443/.554 opponent slash line. That works out to a .997 opponent OPS, the worst mark in the majors.

Let’s take a look at how each D-backs relief pitcher has performed in those crucial innings:

A glaring lack of strikeouts immediately stands out. D-backs relievers have punched out only nine of the 79 hitters they have faced in high-leverage situations, six of which were by interim closer Kevin Ginkel. The rest of their reliever corps has struck out just three out of 57 batters.

While the strikeout issue has been most pronounced in high-leverage situations, it has also been an issue in general. So far this season, Diamondbacks relievers rank 29th in baseball with an 18.8 percent strikeout rate, ahead of only the Kansas City Royals. For reference, Arizona’s bullpen posted a 23.2 percent strikeout rate last year.

Of course, Sewald’s return could fix a multitude of problems. When the Diamondbacks acquired him at the trade deadline last year, they had a 4.63 bullpen ERA. That figure was a much-improved 3.84 the rest of the way, including a 2.16 mark in September. Sewald gave the Diamondbacks much-needed stability in the ninth inning and helped other members of the bullpen settle into more defined roles.

However, even in those final two months in which the bullpen showed significant improvement, the unit far outperformed its underlying metrics. D-backs relievers combined for a 4.51 FIP and 4.42 xFIP from Aug. 1 through the end of the year, which ranked just 19th and 21st, respectively.

All that is to say: While Sewald’s return figures to be a big boost, the notion that he will instantly thrust the Diamondbacks’ bullpen to the top half of the league does not seem like a sure bet.

Another point worth mentioning here is the D-backs’ struggles against left-handed hitters. Lefties are slashing an eye-popping .417/.559/.792 against D-backs relievers in high-leverage situations this year, much of which is due to the early-season struggles of the team’s two primary left-handed relievers up to this point, Nelson and Joe Mantiply.

While Sewald’s return would certainly lessen the load on the lefties in the bullpen, he is not the wipeout left-handed specialist that the team has seemingly lacked so far.

Why the Diamondbacks decided to stand pat in bullpen

When Diamondbacks general manager sat down for his exit interview last November, more than 15 minutes passed before the notion of adding to his bullpen even came up.

Unlike past years, it was not a top priority. The backend of the Diamondbacks’ bullpen was a strength down the stretch, and the team lost a pivotal Game 4 of the World Series in large part because they only had three viable postseason starting pitchers. Adding to the starting rotation was a main priority, as was replacing several hitters that were set to leave in free agency.

Ultimately, the off-season came and went, and the Diamondbacks’ Opening Day bullpen was identical to their World Series bullpen — with one exception: Andrew Saalfrank started the year in Reno and McGough, who was hurt last October, made the team.

When asked at the start of spring training why the team opted not to make any significant bullpen additions, Diamondbacks general manager talked about striking a balance between adding veterans and leaving opportunity open for young pitchers.

“We still have guys in our eyes that could have a chance to come in and take some opportunities,” Hazen said. “I’m looking for guys like [Triple-A reliever] Justin Martinez to come up and harness 100-plus with wipeout secondary stuff and getting into that mix at some point, too. You gotta give some of those opportunities sometimes to see what they can actually do. If we close the door on Kevin Ginkel, if we close the door on Andrew Saalfrank, we never would’ve seen what we saw in the playoffs last year. So, I think there’s a fine line with that.”

In terms of opening the door for young players, Diamondbacks 26-year-old rookie Bryce Jarvis, who made his major-league debut last August, made the team as a long reliever out of spring training and has seen his role grow in importance over the first few weeks of the season. Jarvis has had a lot of traffic on the bases, as indicated by his 1.50 WHIP, but he has held his own with a 3.07 ERA.

Beyond Jarvis, the Diamondbacks have not given any of their other young pitchers an extended look in the bullpen, although Saalfrank, who played a big role last year, was called up prior to Tuesday’s game in St. Louis to replace now injured right-hander Miguel Castro.

Perhaps the Diamondbacks would have tried another one of their young starters in the bullpen by now had it not been for the influx of starting rotation injuries. The team is missing Rodriguez, Ryne Nelson and, most recently, Merrill Kelly, who was placed on the injured list on Tuesday with a right shoulder strain. For now, they have understandably prioritized starting rotation depth, and that has left Hazen with fewer options to work with in the bullpen.

Of course, Hazen could not have predicted that Sewald would miss the first month of the season, or that three starters would be down before May. Perhaps the bullpen situation would be quite different now had those not happened.

It’s also worth mentioning that, while the Diamondbacks spent plentifully this off-season, their resources were still limited. Adding to the bullpen might have meant passing on improvements in other areas, or dealing valuable prospects in a trade. Relievers are more volatile than any other assets in baseball, and investing significant resources in them is risky.

Nonetheless, given how the Diamondbacks’ season has started, one can’t help but wonder if adding a reliever or two over the off-season might have this team in a much better position than it is now.

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Top photo: Rob Schumacher/The Republic