Potential D-backs Free Agency Target: David Robertson

Should the Diamondbacks pursue a contract with the veteran closer who has excelled in recent years?

Sep 29, 2024; Anaheim, California, USA; Texas Rangers relief pitcher David Robertson (37) pitches during the ninth inning against the Los Angeles Angels at Angel Stadium. Mandatory Credit: Kiyoshi Mio-Imagn Images / Kiyoshi Mio-Imagn Images

This article is part of a series evaluating potential free agent and trade acquisitions for the Arizona Diamondbacks entering the 2025 season.

The Diamondbacks kicked off their off-season on December 21 when they acquired Josh Naylor from the Cleveland Guardians to replace star Christian Walker who left for Houston.

After making the trade, GM Mike Hazen spoke in depth about being involved in the back-end reliever market and wanting to upgrade the bullpen. That is likely where the team's focus lies now.

While the closer role for the D-backs has been a bit of a rollercoaster, the team seemed to operate best when there was a single legitimate closer at the back-end such as Paul Sewald for the end of 2023 and beginning of 2024.

Manager Torey Lovullo and Hazen have both spoke about the importance of having a single closer in the past despite having a trio of back-end arms such as Justin Martinez, A.J. Puk, and Kevin Ginkel.

Martinez might not be ready for a full-time closer role and Puk is too valuable to use at big moments in the 7th and 8th innings to hold him just for the 9th inning, so a closer is a top need.

With the budget tightened due to the team's inability so far to deal Jordan Montgomery and his $22.5 MM contract, Diamondbacks ON SI's Jack Sommers estimated Sunday that the D-backs have between $17-22 million to spend.

That's to find a utility player, a reliever or two, and a right-handed slug hitter that can most likely play outfield and DH.

With uncertainties in the rotation, an elite bullpen could do wonders for the team's ability to win games in 2025 and that's exactly what the D-backs seeming to be aiming towards make happen.

RHP, David Robertson - Free Agent, Texas Rangers

One of the oldest free agents on the market, yet one of the most proven relief arms with plenty of late-game experience, a high fastball, and a proven track record.

His age will limit his contract to one year offers and the salary will be high, but the veteran traveler, five teams in three years, would be hard to pass up if he can continue to replicate his sterling results.

Pros

Results and Track Record

Robertson had a standout year with the Rangers in 2024. Over 68 games, he had just a 3.00 ERA, 132 ERA+, 2.65 FIP, 3.22 xERA, and 2.88 xFIP. His fWAR was 1.9. He struck out 99 batters in just 72 innings while walking only 27.

His 33.4% strikeout rate was excellent and there wasn't much luck to his ERA numbers being that low thanks to a BABIP of .300. He wasn't lucky with men on base as his left on base stranded percentage was right in line with his career norm with 76.9% this year.

When going back three seasons, Robertson has pitched in 188 games and thrown 201 innings. He's finished 77 games and recorded 40 saves. Over that time, he pitched to a 2.82 ERA and 147 ERA+. He's been a lethal pitcher out of the bullpen lately.

Baseball Savant Darling

Per his Baseball Savant page, Robertson had a strong year in 2024 with the advanced analytics. His fastball run value was 19, in the 97th percentile.

Meanwhile, his overall pitching run value of 13 was in the 86th percentile. His xERA and xBA were both in the 84th percentile. Meanwhile, he got whiffs at a 29.5% rate, the 79th percentile, which helped lead his strikeout rate to be in the 96th percentile.

He achieved high marks for his ability to avoid the barrel of the bat, garner ground balls, and his extension.

Opponents hit just .163 against his cutter while their expected batting average against his slider was just .226. All told, there's plenty to like when digging deeper into his stats.

Cost

Robertson would be limited to a one-year deal thus preventing any long-term pay issues for the Diamondbacks, unlike say Jeff Hoffman or Tanner Scott, who will require deals of at least three years.

Fangraphs predicts a one year deal worth $10 MM for Robertson although their projections this year have tended to come on the low end with most deals going higher.

Still, Robertson is unlikely to get more than $12 MM at most, and for a one year deal that would be a solid bet on his potential to be a back-end reliever who has 177 career saves.

While it would eat up a large chunk of the money left to spend, this is the going rate for a good late-inning reliever that can close. Those types of players simply aren't cheap to sign in free agency.

Cons

Age

Robertson just completed his age-39 season. The 2025 season would be his age-40 season. That's an old age in baseball, especially for the shoulder and elbow of a pitcher.

There's no telling when his velocity could drop off due to Father Time and age-related decline. Despite his age, his fastball has gotten faster since 2021 when it averaged 92.1. Last year, it averaged 93.3 mph.

However, Father Time is undefeated and as the D-backs saw with former elite closer Mark Melancon, the drop off in skill and velocity can be sudden and quick.

No reliever in the pitch tracking era has thrown a harder cutter than David Robertson's in his age 39 season when he averaged 93.3. But even the great Mariano Rivera went from 93.5 in his age 38 season to 91.9 at age 39. Mark Melancon dropped from 92 to 90.9 from age 36 to 37.

Pitchers at this age can lose 1-2 MPH seemingly overnight. This is a hurdle that Robertson will have to overcome.

Also of note is that nobody since 2017 who is 40 years or older has had a wOBA against under .300. Robertson could be a unicorn but that's a tough precedent to beat.

Additionally, only one reliever in their 40's over the last decade has pitched at least 30 innings and that reliever is Jesse Chavez. Yet another challenge to surpass.

While it would appear that Robertson should have another strong season in 2025 based off of his results in 2024 and the few years prior, it's simply a major risk to trust that he will be the same pitcher or that his body will hold up to the wear and tear.

Lack of Chase

There's one glaring issue for Robertson despite his eye-popping strikeout rates. He simply doesn't get batters to chase at pitchers very often.

He was in the 15th percentile for inducing chase, which foretells struggles ahead if he stops obtaining the swing-and-miss that he's relied upon or loses his pinpoint control. If either of those two things happen, Robertson could indeed see a dramatic drop-off in results.

Conclusion

David Robertson is a savvy veteran pitcher that has experienced plenty of success in recent years. Despite being in his age-39 season, he put up one of the best seasons of his career with the Rangers.

There's no doubt that if he can continue to stay effective in 2025, he would be a major asset to the D-backs bullpen whether as a closer or 8th inning pitcher. His strikeout rate would get the Diamondbacks out of plenty of jams.

However, he would cost over $10 MM and is entering his age-40 season. Very few pitchers experience much success once they turn 40. There's a very real chance that he doesn't obtain much success in 2025 due to age related decline.

David Robertson has had a terrific career and the Arizona Diamondbacks could certainly use a player of his skill on their roster. But, it's a risk they would have to be comfortable taking considering the clear downside that could happen.

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