10 formidable relief pitchers that Diamondbacks could target this winter

Diamondbacks general manager Mike Hazen would like to add to the backend of his bullpen this offseason, but it remains to be seen what form that will take.

Is the team content with a middle relief/setup arm? Is it willing to invest in an established closer? Could the Diamondbacks make a splash and acquire one of the top relievers on the market? The answers to these questions will become clearer as the offseason progresses.

When assembling this list of potential targets, I focused primarily on relievers with recent closing experience. That is not to say that the Diamondbacks do not have any internal candidates for that job — right-hander Justin Martinez filled in admirably after Paul Sewald lost the role in August — but Martinez is just 23 years old and entering his second full season.

Another closer candidate, left-hander A.J. Puk, has relatively little experience in the role. He also might be better used earlier in games, when the Diamondbacks can match him up against opposing teams’ best left-handed hitters. Acquiring a closer might not be a necessity, but it would add stability.

After giving it some thought, I decided to leave the top two free agent relievers, left-hander Tanner Scott and right-hander Jeff Hoffman, off the list. That is not to say that the Diamondbacks have no chance of signing them, but both are widely expected to get over $40 million guaranteed in free agency. The Diamondbacks have never committed more than $14 million to a free agent reliever in franchise history. (See Mark Melancon in 2021.) It seems unlikely that they would land either of them.

Of the 10 options listed below, the first five are trade candidates and the next five are free agents. Let’s dive in.

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1. Ryan Helsley, St. Louis Cardinals

Only one National League reliever received Cy Young votes in 2024: St. Louis Cardinals closer Ryan Helsley.

Helsley, 30, posted a 2.04 ERA, 1.10 WHIP and 79 strikeouts to 23 walks over 66.1 innings in 2024. He led baseball with 49 saves and had a stellar 92.5 percent conversation rate (49-of-53).

With the Cardinals reportedly looking to get younger, Helsley appears to be one of the more likely players to be moved this offseason. He is under club control for one more season, and is projected by MLB Trade Rumors to make $6.9 million in arbitration.

Helsley throws a four-seam fastball, slider and occasional curveball. While his strikeout rate has dropped each of the past two seasons, his underlying whiff rate has remained essentially unchanged. Helsley’s four-seamer averaged 99.6 mph in 2024, which is in line with his velocity from 2022-23.

The fact that Helsley only has one year remaining before free agency is an obvious drawback, and perhaps a dealbreaker for the Diamondbacks.

Since taking over as Diamondbacks GM in 2016, only once has Hazen made an offseason trade for a player with one year of club control. That happened in December 2022, when the Diamondbacks acquired outfielder Lourdes Gurriel Jr. as part of a three-player deal with the Toronto Blue Jays. Gurriel was a secondary piece, however; the prize of the trade for the Diamondbacks was catcher Gabriel Moreno, who came with six years of club control.

Trading significant pieces solely for one year of Helsley would be unlike anything Hazen has done before in the offseason.

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2. Devin Williams, Milwaukee Brewers

For as good as Ryan Helsley has been in recent years, Milwaukee Brewers closer Devin Williams has arguably been better.

Among MLB pitchers who have logged 200 or more innings since 2020, Williams’ .144 opponent batting average ranks first, his 1.70 ERA ranks second and his 40.8 percent strikeout rate ranks third. His four-seam fastball averages around 95 mph, and his mid-80s changeup is basically unhittable.

Williams missed four months with a back injury in 2024, but was otherwise his usual dominant self. In 21 2/3 innings, he had a 1.25 ERA, 0.97 WHIP and 38 strikeouts compared to 11 walks. He went 14-of-15 in save opportunities.

Like Helsley, Williams is entering his final year of salary arbitration and seems fairly likely to be traded. Earlier this month, the small-market Brewers declined Williams’ $10.5 million club option for 2025. He is still under control for one more season via arbitration, and is projected to make $7.7 million.

Again, given that Wiliams has only one year of club control remaining, the Diamondbacks might be hesitant to part with significant assets to acquire him.

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3. Andres Muñoz, Seattle Mariners

The Diamondbacks got their previous closer, Paul Sewald, from the Seattle Mariners at the 2023 trade deadline. Could they get their get next closer from the Mariners, too?

Mexican right-hander Andres Muñoz, 25, is coming off another stellar season in 2024. In 59 1/3 innings, he posted a 2.12 ERA, 0.96 WHIP and 77 strikeouts to 26 walks. He went 22-of-27 in save opportunities.

Unlike Helsley and Williams, Muñoz has plenty of club control remaining. He signed an extension with Seattle following the 2021 season, and is under contract through 2028. He is slated to make $2.5 million in 2025, and has club options for the 2026-28 seasons at $6 million, $8 million and $10 million, respectively.

Granted, it does seem unlikely that the Mariners would trade an elite reliever who still has four years of control remaining. However, it also seemed unlikely that the Mariners would trade closer Edwin Díaz in 2018 when he also had four years of control remaining. But that is exactly what happened.

Muñoz’s upper-80s slider graded out as one of the best sliders in baseball in 2024. He also throws a four-seamer and sinker. While Muñoz’s velocity has decreased about 1 mph each of the past two seasons, he still averaged 98.4 mph on his four-seamer and 97.5 mph on his sinker in 2024.

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4. Pete Fairbanks, Tampa Bay Rays

Tampa Bay Rays right-hander Pete Fairbanks could be a buy-low candidate for the Diamondbacks this winter.

After back-to-back seasons as one of the best relievers in baseball, Fairbanks turned in a middling 2024 season by his standards. In 45 1/3 innings, he had a 3.57 ERA, 1.17 WHIP and 44 strikeouts to 17 walks. He went 23-for-27 in save opportunities.

Fairbanks finished the year on the injured list due to a right lat strain that he suffered in mid-August. It was his second lat strain in the past three years. He is expected to be healthy for spring training of 2025.

The 30-year-old veteran is expected to make around $3.8 million in 2025 and has a club option for 2026 at $7 million plus potential bonuses.

While Fairbanks’ recent injury history is somewhat troubling — he also missed about three weeks in 2024 with nerve-related issues in his throwing arm — those injures could explain why his velocity took a turn for the worse. After averaging 99 mph on his four-seamer in both 2022 and 2023, Fairbanks averaged 97.3 mph on the pitch in 2024. With a healthy offseason, perhaps Fairbanks could return to form as one of the better closers in the game.

The Rays are walking through a tumultuous stadium situation in the aftermath of Hurricane Milton, and seemingly all of their players with limited club control, including Fairbanks, could be available in the right deal.

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5. Ryan Pressly, Houston Astros

Entering his age-36 season, Houston Astros right-hander Ryan Pressly is not the dominant force that he once was, but he has a strong track record as a backend reliever.

After serving as the Astros’ primary closer from 2020-23, Pressly was demoted to a setup role in 2024. He turned in a solid 3.49 ERA and 1.34 WHIP in 56.2 innings.

Pressly will make $14 million in 2025 and has a $14 million mutual option with a $2 million buyout for 2026. With how his underlying stats are trending, the Astros would likely have to eat money to facilitate a deal.

Pressly’s strikeout rate has plummeted from 35.7 percent in 2022 to 27.6 percent in 2023 to 23.8 percent in 2024. A four-seamer that once averaged 96 mph with excellent vertical ride now averages 94 mph with a fairly unremarkable movement profile.

Nonetheless, unlike many of the other trade options presented here, Pressly figures to command a fairly modest return. He might not be an ideal closing option at this stage in his career, but he could still provide valuable depth.

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6. Carlos Estévez, free agent

At age 31, right-hander Carlos Estévez turned in the best season of his career.

In 55 innings with the Los Angeles Angels and Philadelphia Phillies in 2024, the veteran right-hander had a 2.45 ERA and 0.91 WHIP and went 26-for-31 in save opportunities. The Phillies paid a hefty price to acquire him at the trade deadline.

Under the hood, there are reasons to wonder if Estévez’s 2024 breakout was sustainable. His 23.6 strikeout rate was actually four ticks lower than in the prior season. He did have the lowest walk rate of his career at 5.7 percent, but he struggled to generate chase. Estévez’s four-seamer averaged a healthy 96.8 mph in 2024, but he lacks an elite secondary pitch.

In the long run, Estévez might be better viewed as a decent closer than an excellent one. Even if that’s the case, there is still plenty of value to be had here.

MLB Trade Rumors projects Estévez to receive a three-year, $27 million contract this winter.

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7. Blake Treinen, free agent

When healthy, few relievers have been as effective in recent years as right-hander Blake Treinen.

After pitching all of five major-league innings from 2022-23 due to shoulder injuries, Treinen, 36, returned to the Los Angeles Dodgers in 2024 and posted a 1.93 ERA, 0.94 WHIP, 30.6 percent strikeout rate and 6 percent walk rate in 46 2/3 innings. Treinen also came up huge for the Dodgers in the playoffs, recording three saves with a 2.19 ERA over 12 1/3 innings, including 2 1/3 scoreless in the Game 5 clincher in New York.

Treinen no longer throws in the upper-90s — his sinker averaged 94.6 mph in 2024 — but he keeps hitters uncomfortable with a four-pitch mix that includes a sweeper, sinker, four-seamer and cutter. The sweeper graded out as one of the best in baseball in 2024, with a 49.2 percent whiff rate.

The Diamondbacks do not often target pitchers with injury reports as long as Treinen’s, but his ceiling is perhaps as high as anyone on this list. Given his injury history and age, it might only take a one-year deal to get him.

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8. Kenley Jansen, free agent

There are three guarantees in life: death, taxes and Kenley Jansen converting 85 percent of his save opportunities by throwing 85 percent cutters. For the 37-year-old, 2024 was more of the same.

In 54 2/3 innings for the Boston Red Sox in 2024, Jansen had a 3.29 ERA, 1.06 WHIP, 28.4 percent strikeout rate and 9.2 percent walk rate. He converted 29 of 33 save opportunities. At this stage in his career, he is not elite, but he has been exceptionally reliable.

Jansen’s signature cutter averaged 92.2 mph in 2024, down two ticks from a spike in 2023, but essentially identical to its average from 2018-22. He is not missing as many bats or barrels with it as he once did, but its unique shape continues to keep hitters off balance.

Jansen will enter 2025 looking to add to his career saves total of 447, which ranks fourth all-time. He trails only Mariano Rivera (652), Trevor Hoffman (601) and Lee Smith (478). Entering his age-37 season, Jansen could probably be had on a one-year deal.

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9. Clay Holmes, free agent

Clay Holmes spent most of the 2024 season as the New York Yankees’ closer, but he lost the role in September, a month in which he allowed six runs in nine innings.

Nonetheless, the 31-year-old was still rather productive in his walk year. Over 63 innings, he posted a 3.14 ERA and 1.30 WHIP, with a 25.1 percent strikeout rate and 8.1 percent walk rate. He followed that up with a 2.25 ERA in 12 innings during the Yankees’ run to the World Series.

Holmes features a sinker, slider and sweeper. His sinker averaged 96.6 mph in 2024 — close to his career high of 97 mph in 2022 — but it got knocked around a bit, with a .317 batting average against. Opposing hitters hit just .133 and .172 against the slider and sweeper, respectively, with excellent whiff rates on each.

While Holmes typically does not post elite strikeout rates, he does keep the ball on the ground. His 64.6 percent ground-ball rate in 2024 ranked in the 100th percentile. He allowed just four homers all year, and has never allowed more than five homers in any season in his career.

Entering his age-32 season, Holmes figures to command a multi-year deal in free agency. MLB Trade Rumors projects three years, $30 million.

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10. Kirby Yates, free agent

Kirby Yates is the oldest player on this list, but he is also coming off one of the better seasons by a reliever in recent memory.

After signing a one-year, $4.5 million deal with the Texas Rangers last offseason, Yates logged a ridiculous 1.17 ERA and 0.83 WHIP in 2024 over 61 2/3 innings. His microscopic .111 opponent batting average was the lowest single-season mark (min. 60 innings) by any major-league pitcher in the Divisional Era (since 1969).

Yates did not open the year as the Rangers’ closer, but it did not take long for him to earn that role. He finished the year 33-for-34 in save opportunities.

While 2024 was Yates’ best season ever, it was not a complete outlier. In 2019, he posted a similar 1.19 ERA and had 41 saves for the San Diego Padres. He also had a 2.14 ERA in 63 innings in 2018. Yates hardly pitched from 2020-22 due to elbow trouble. He had Tommy John surgery in March of 2021.

Yates does not have stand-out velocity — his four-seamer averaged 93.2 mph in 2024 — but his fastball has never averaged over 93.9 mph at any point in his career. That heater tunnels extremely well with his splitter, forming a deadly two-pitch combo.

The team that signs Yates probably shouldn’t expect a low-1s ERA moving forward, but he figures to be a highly-sought-after commodity after the season that he just had. A one-year deal seems likely given his age, but it could be pricey. MLB Trade Rumors projects one year, $14 million.

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