No general manager in all of Major League Baseball is perfect. Arizona Diamondbacks GM Mike Hazen is not an exception to that rule.
Like any, Hazen had his fair share of success stories, alongside transactions he'd likely want back if given the chance to do them over.
Let's rank his three biggest successes, and the three risks that did not pay off for Arizona in the 2026 regular season.
Sep 26, 2026; San Diego, California, USA; Arizona Diamondbacks relief pitcher Jonathan Loaisiga (43) throws a pitch during the first inning against the San Diego Padres at Petco Park. Mandatory Credit: David Frerker-Imagn Images | IMAGN IMAGES via Reuters Connect
After the Diamondbacks' bullpen was one of the largest detractors to their success in previous years, Hazen made moves to upgrade in that area - despite both A.J. Puk and Justin Martinez waiting to come off the IL.
But moves Hazen made worked out very well.
Jonathan Loaisiga was a minor league signing. He pitched the best season of his career since 2021 with the Yankees, producing a 2.42 ERA in 67.1 innings . Taylor Clarke cost just over $1.5 million and pitched to a 2.96 ERA in 70.2 innings.
Even the Paul Sewald reunion worked out to a degree. Though Sewald struggled heavily on his way out, the veteran closer held down the ninth inning with 24 of 27 saves converted before Arizona pivoted to a committee approach .
Sep 25, 2026; San Diego, California, USA; Arizona Diamondbacks third baseman Nolan Arenado (28) hits a two-run home run during the third inning against the San Diego Padres at Petco Park. Mandatory Credit: Denis Poroy-Imagn Images | IMAGN IMAGES via Reuters Connect
If one were to hear that Nolan Arenado led his team in home runs, one might assume they'd gone back in time. That is essentially what Arenado did this year.
Hazen acquired the 35-year-old future Hall Of Fame third baseman ahead of the year in a trade with the Cardinals. Arizona only sent over unranked pitching prospect Jack Martinez, while St. Louis surrendered Arenado and paid most of his salary.
The D-backs only paid Arenado $5 milion, but got a resurgent 30-homer season and a .806 OPS alongside high-level third base defense. He's under contract for $6 million next year.
Sep 27, 2026; San Diego, California, USA; Arizona Diamondbacks catcher James McCann (8) hits a single during the seventh inning against the San Diego Padres at Petco Park. Mandatory Credit: Denis Poroy-Imagn Images | IMAGN IMAGES via Reuters Connect
The Diamondbacks brought veteran catcher James McCann back for just $2.75 million this offseason, and he produced on both sides of the ball despite some injury-related downtime.
McCann hit .282/.311/.455 for a .766 OPS , played good defense and maintained his steady, veteran leadership. He worked well with Arizona's starters and allowed Gabriel Moreno to get some DH days, which led to a career season from Moreno.
Having a strong backup catcher option is no small feat. McCann was about as good as it gets for an affordable price.
Apr 2, 2026; Phoenix, Arizona, USA; Arizona Diamondbacks first baseman Carlos Santana (41) makes a play at first during the fourth inning at Chase Field. Mandatory Credit: Arianna Grainey-Imagn Images | IMAGN IMAGES via Reuters Connect
The Diamondbacks' roster looked a bit thin with regard to first base ahead of 2026. Arizona needed some slug from that position and got nearly nothing .
Hazen tried to make it work with a Carlos Santana-Pavin Smith platoon at first base, but those players struggled and spent time injured.
Ildemaro Vargas, Tim Tawa and Jose Fernandez did some good things at times, but it was clear from Arizona's league-worst .636 first base OPS that the D-backs needed to invest a bit more heavily in that position this year.
DH was a similar story. Arizona needed lefty slug and didn't get much of that. Hazen tried to remedy it with Max Kepler, Jesus Sanchez and in-house options, but those endeavors were unproductive.
Aug 25, 2026; Phoenix, Arizona, USA; Chicago Cubs pitcher Clay Holmes against the Arizona Diamondbacks at Chase Field. Mandatory Credit: Mark J. Rebilas-Imagn Images | IMAGN IMAGES via Reuters Connect
Hazen does not control the trade market, but the Diamondbacks desperately needed starting pitching help at the deadline, and they could not get it . It was not for lack of trying, but a deal with the Mets regarding Clay Holmes fell through .
It's tough to pin this entirely on Hazen, given how the market shook out.
But Arizona had to spend far too many games attempting to recover from poor starts by rookies like Kohl Drake, Jose Cabrera and Mitch Bratt. Zac Gallen and Merrill Kelly were ineffective and banged up.
The D-backs needed pitching, but instead only managed to secure Lars Nootbaar. That trade is nuanced and not featured here for various reasons, though a breakdown can be read here.
Jul 1, 2026; Phoenix, Arizona, USA; Arizona Diamondbacks pitcher Zac Gallen (23) throws against the San Francisco Giants in the first inning at Chase Field. Mandatory Credit: Rick Scuteri-Imagn Images | IMAGN IMAGES via Reuters Connect
The idea was the Diamondbacks could bring back one of Gallen or Kelly ahead of the season. Most assumed it would be Kelly, especially after he signed a lucrative two-year, $40 million deal to come back to Arizona.
But then Gallen followed on a deferred deal worth just over $22 million.
At the time it seemed like a depth-providing transaction, but neither arm ended up providing much positive value. Gallen struggled to an even worse 6.07 ERA and provided almost no value. Kelly had an extremely up-and-down season that resulted in a 4.94 ERA over 162 innings.
Kelly may be able to bring back the old version of himself in the coming seasons. But at 38 years old, that is becoming more of a question. Gallen has likely run his course with this organization.
This article was originally published on www.si.com/mlb/diamondbacks/onsi as Ranking D-backs GM Mike Hazen's Biggest Successes, Failures of 2026 .
