The Arizona Diamondbacks are set to include right-handed pitcher Jonathan Loaisiga on their Opening Day roster, as reported by Jorge Castillo of ESPN. However, because Arizona’s 40-man roster is already at capacity, the organization will need to make a corresponding move before Loaisiga’s contract can be formally selected and finalized.
At 31 years old, Loaisiga is embarking on a new chapter in his professional career, marking the first time he will suit up for a club other than the New York Yankees. His journey to this point has been anything but straightforward.
Originally signed out of Nicaragua by the San Francisco Giants in 2013, Loaisiga’s early development was derailed by injuries. He managed to make only 13 starts for the Giants’ Dominican Summer League affiliate before health issues sidelined him for two consecutive seasons. Ultimately, those setbacks led to his release in 2015, leaving his professional future uncertain.
Despite that rocky beginning, Loaisiga found a second opportunity when the Yankees signed him prior to the 2016 season. From there, he steadily worked his way through the minor league system, initially developing as a starting pitcher. When he reached the majors, he was used in a hybrid role, alternating between starting and relieving appearances. That flexibility allowed him to carve out a place on the roster, but it wasn’t until later in his career that he truly found his niche.
Loaisiga’s transition to a full-time relief role didn’t occur until the 2021 season, but once he made that shift, his performance improved dramatically. That year, he emerged as one of the most effective bullpen arms in baseball. Over the course of 70 2/3 innings, he posted an outstanding 2.17 ERA, supported by equally impressive advanced metrics such as a 2.58 FIP and a 3.01 SIERA.
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His ability to miss bats was solid, as he struck out 24.4% of opposing hitters, while maintaining excellent control with a walk rate of just 5.7%. Perhaps most notably, he generated ground balls at an elite rate of 60.9%, making him extremely difficult for hitters to square up.
That dominant 2021 campaign elevated Loaisiga into high-leverage situations for the Yankees, and expectations were high heading into the following season. Many observers believed he had the potential to become one of the premier relievers in the league. Unfortunately, his performance in 2022 did not live up to those expectations.
He struggled to replicate his prior success, finishing the year with a 4.13 ERA, which fell below league average. While his underlying metrics, including a 3.57 FIP and 3.76 SIERA, suggested he wasn’t quite as ineffective as his ERA indicated, it was still a noticeable step back from his breakout season.
In the years that followed, Loaisiga’s progress was further hindered by a series of injuries. Over the next three seasons, he appeared in just 50 major league games, limiting his ability to establish consistency or regain his previous form.
Although he managed to post a respectable 3.51 ERA during that stretch, a deeper look at his performance reveals several concerning trends. His ground ball rate declined to 52.0%, a significant drop from his peak. Even more troubling was his reduced strikeout rate, which fell to 15.2%, indicating diminished effectiveness in generating swings and misses.
Advanced metrics paint an even clearer picture of his struggles. Loaisiga’s 5.13 FIP and 4.09 SIERA suggest that his run prevention during that period may have been aided by favorable outcomes on balls in play and sequencing, rather than dominant pitching. In other words, while his ERA remained serviceable, it did not fully reflect the underlying decline in his performance.
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Given the combination of injury concerns and declining effectiveness, it was not surprising that Loaisiga entered the offseason without a guaranteed major league contract. Instead, he had to settle for a minor league deal. Even so, his agreement with the Diamondbacks presented a promising opportunity. Arizona’s bullpen situation heading into the season created a pathway for him to make the team, particularly with several key late-inning relievers expected to begin the year on the injured list.
Loaisiga took advantage of that opportunity during spring training, delivering a solid performance that helped secure his spot on the roster. Across seven appearances, he posted a 3.86 ERA while recording seven strikeouts and issuing only two walks. While those numbers may not be eye-popping, they were sufficient to demonstrate that he still has the ability to contribute at the major league level.
As a result, Loaisiga will open the season as a member of the Diamondbacks’ bullpen, where he is likely to receive opportunities in meaningful situations. With several established relievers unavailable to start the year, there is a chance for him to earn a role in high-leverage scenarios if he performs well.
He will be part of a group of pitchers competing for late-inning responsibilities, including Paul Sewald, Ryan Thompson, and Kevin Ginkel. Each of these arms brings different strengths to the bullpen, and the team will likely evaluate their performances closely as the season progresses.
Looking ahead, the bullpen picture could change as injured players return. Both A.J. Puk and Justin Martinez are expected to rejoin the team at some point during the season, which would add further competition for high-leverage roles. Until then, however, Loaisiga has a valuable opportunity to reestablish himself as a reliable late-inning option.
In many ways, this move represents both a fresh start and a critical moment in Loaisiga’s career. After years of battling injuries and inconsistency, he now has a chance to prove that he can still be an impactful pitcher at the highest level. If he can rediscover the form that made him so dominant in 2021, he could become a key contributor for the Diamondbacks. On the other hand, continued struggles could make it difficult for him to maintain a spot on the roster once the team returns to full health.
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For the Diamondbacks, the decision to bring Loaisiga into the fold reflects a low-risk, potentially high-reward strategy. By signing him to a minor league deal and giving him an opportunity to earn a roster spot, they have added a pitcher with proven upside without making a significant financial commitment. If he performs well, the team stands to benefit from his experience and ability. If not, they can move on with minimal consequences.
Ultimately, Loaisiga’s inclusion on the Opening Day roster highlights both the uncertainty and opportunity that define bullpen construction in Major League Baseball. With roles often in flux and performance subject to rapid changes, pitchers like Loaisiga can quickly rise—or fall—based on their ability to adapt and execute. As the season begins, all eyes will be on whether he can take advantage of this opportunity and once again establish himself as a dependable arm in a major league bullpen.
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