Diamondbacks seeking bullpen help with key relievers on IL

The D-backs announced Thursday that they’ve placed closer Justin Martinez on the 15-day injured list due to right shoulder inflammation. Lefty Jose Castillo’s contract was selected from Triple-A Reno to take his spot on the active roster. Fellow southpaw A.J. Puk moves from the 15-day IL to the 60-day IL to create 40-man roster space for Castillo.

Martinez was set for an MRI this morning after experiencing an alarming velocity drop over the past week. He’s gone from averaging triple digits on his power sinker to sitting just 93.5 mph in his most recent appearance. Though the right-hander claimed he felt 100% healthy, he’ll head to the injured list with a still-vague injury designation. The D-backs will surely provide more information on his status and potential timeline later today.

This slate of injury-related moves is a brutal blow for a D-backs team that spent much of the offseason looking for established bullpen arms but wound up making generally smaller-scale moves. Martinez and Puk are the team’s two best relievers and entered the year as the favorites to work in save and high-leverage hold situations. They’re both on the shelf, and while Puk’s flexor strain won’t require surgery, today’s move to the 60-day IL only further underlines the fact that Arizona is going to be without him for quite some time.

Martinez, 23, averaged 100.2 mph on his sinker in 2024 and averaged better than 100 mph on the pitch in each of his first eight appearances this year. A dip into the 97-99 mph range over his next three outings was concerning but not necessarily cause for full-fledged alarm. Last night’s drop all the way to 93.5 mph, in an outing where he faced three hitters and allowed two walks and a home run, is another story entirely.

It’s become an ominous situation for D-backs fans to monitor, and one that’s compounded by Puk’s absence. Martinez broke out with a 2.48 ERA, 29.5% strikeout rate, 11.7% walk rate, 58.9% ground-ball rate, eight saves and seven holds across 72 2/3 innings for the Snakes last year. He clearly has some command issues, but the elite velocity coupled with plus strikeout and ground-ball rates helped to mitigate that bloated walk rate.

The D-backs, clearly bullish on Martinez’s future, signed him to a five-year, $18MM extension during spring training. The contract contains a pair of club options for the 2030-31 seasons, which would’ve been Martinez’s first two free agent years. At the time, there was little reason to fear an injury (beyond the general attrition rate of pitchers in today’s game). Now, the outlook is far hazier.

Were Puk healthy, the Diamondbacks would surely have just plugged him into the closer’s role and moved forward with Kevin Ginkel setting up. But Puk hit the injured list with elbow inflammation after a strong eight-inning start to his 2025 season, and a subsequent MRI revealed a flexor strain that’ll require a notable shutdown period.

With Martinez and Puk both shelved, the D-backs will likely turn closing duties over to a combination of Ginkel and Shelby Miller, who returned to Arizona on a minor league deal this offseason and has been outstanding after earning a job this spring. Ginkel only just returned from his own bout of shoulder inflammation, which sidelined him for the first month of the season. From 2022-24, he pitched a combined 164 2/3 innings with a 2.95 ERA, 26.1% strikeout rate and 7.9% walk rate. Miller has pitched 12 2/3 scoreless innings in his return to Phoenix, punching out a gaudy 31.9% of opponents against an 8.5% walk rate.

The 29-year-old Castillo isn’t likely to replicate the type of results that could’ve been expected from either Martinez or Puk, but he’s a reasonably experienced southpaw who’s had some prior success in the majors. Back in 2018-19, the southpaw looked to be breaking out as a viable bullpen arm for the division-rival Padres, pitching to a combined 3.23 ERA with a 35% strikeout rate and 8.4% walk rate in his first 39 big league innings.

Injuries have blown up Castillo’s career since. He suffered a torn ligament in his hand that cut his 2019 season short. A torn lat wiped out his 2020 season. He underwent Tommy John surgery in 2021 and missed most of the 2022 season as a result. It’s a staggering run of unfortunate maladies for the southpaw, but he’s shown some encouraging signs since joining the D-backs on a minor league deal last year.

In 24 innings between Arizona’s Rookie-ball and Triple-A affiliates last year, Castillo notched a 3.75 ERA. He whiffed 24.1% of his opponents and issued walks at an 8.1% clip with Triple-A Reno. This year, he’s started out by holding opponents to a run on four hits and no walks with seven strikeouts in 5 1/3 frames. Castillo has had an arduous grind to get back to the majors after pitching just two MLB frames from 2019-23. He’s now poised for his first real look in a bullpen since 2018, despite accumulating four years of MLB service time through his various stints on the 60-day injured list.

Because he only has four years of service, Castillo could be a multi-year option for Arizona if he can get back to his early career form. Enough time has already elapsed that he won’t be able to reach five years of service before the conclusion of the 2025 season. That means even if he’s back in the majors for good — and that’s far, far from certain — he can be controlled through the 2027 campaign via arbitration.