Signing Angels' All-Star Closer Would Be Massive Risk for D-backs

The Arizona Diamondbacks need to take the ninth inning seriously, but one of the premier options comes with heavy risk.

Sep 26, 2025; Anaheim, California, USA; Los Angeles Angels pitcher Kenley Jansen (74) celebrates the victory against the Houston Astros at Angel Stadium. Mandatory Credit: Gary A. Vasquez-Imagn Images | Gary A. Vasquez-Imagn Images

It's 2025 (soon to be 2026) and the Arizona Diamondbacks still need a closer. The ninth inning has been a perpetually-tortuous ride for D-backs fans, year in and year out, and this past season was no different.

Of course, that is partially due to the loss of both A.J. Puk and Justin Martinez to Tommy John Surgery. Both of those arms will be out much of 2026, as well.

The D-backs need a defined ninth-inning arm, and a certain Los Angeles Angels former All-Star closer is set to hit the free agent market — right-hander Kenley Jansen.

Jansen's overall results were positive. He would have immediately been the best healthy reliever in the D-backs' bullpen in 2025. But would he be a smart signing for 2026? A look underneath offers some concerns.

Is Kenley Jansen a Fit For Diamondbacks?

Sep 24, 2025; Anaheim, California, USA; Los Angeles Angels relief pitcher Kenley Jansen (74) earns his 28th save of the season in the ninth inning against the Kansas City Royals at Angel Stadium. Mandatory Credit: Jayne Kamin-Oncea-Imagn Images | Jayne Kamin-Oncea-Imagn Images

First, let's examine the positive, surface-level numbers. Jansen got the job done over and over for the Angels in 2025, converting an unbelievable 29 of his 30 save opportunities.

His 2.59 ERA and .175 average against were his best since the 2021 season. His 0.95 WHIP was his best since 2018. Despite being 37 years old, he remained healthy for the entirety of 2025, making 62 appearances.

In terms of overall results, and the fact that he's a savvy veteran with four All-Star nods who simply knows how to work a ninth inning, Jansen would likely be a positive addition to a leaky D-backs bullpen.

However, there are some serious concerns — concerns that convert a Jansen signing from a slam-dunk to a considerable risk.

Why Kenley Jansen is Huge Risk for Diamondbacks

Jul 9, 2025; Anaheim, California, USA; Los Angeles Angels relief pitcher Kenley Jansen (74) tosses the ball on the mound during the ninth inning against the Texas Rangers at Angel Stadium. Mandatory Credit: Jayne Kamin-Oncea-Imagn Images | Jayne Kamin-Oncea-Imagn Images

Signing a veteran closer with significant mileage has not always worked in Arizona's favor.

Fans of the D-backs need no reminder of the franchise's many attempts at such an addition, though Mark Melancon and the 2024 version of Paul Sewald are the most recent examples.

But Jansen's peripherals suggest his 2025 success was extremely providential. His 3.98 FIP (Fielding Independent Pitching) undermined his 2.59 ERA, while his expected ERA (xERA) was 3.78.

That 1.39-run discrepancy between his ERA and FIP is the widest of his career.

Average exit velocity against the righty was 91.5 — a bottom 3% number across MLB, per Statcast. While he did collect whiffs and chases at around the league average rate, he was hit quite hard all year.

That hard contact simply found gloves at an inordinate rate. Jansen's BABIP (Batting Average on Balls in Play) against was .195 — a truly astonishing (and completely unsustainable) figure. It was the lowest of his entire career by nearly 20 points.

Jansen also stranded 85.2% of baserunners — his best since 2017, and also a likely unsustainable clip.

While his signature cutter (used 82% of the time in 2025) hasn't lost much in terms of velocity, its movement suffered a great deal. The pitch was significantly straighter this past season, without as much late glove-side bite.

Opponents hit it to just a .163 average, but its expected slug (.463) and expected wOBA (.322) both vastly surpassed the raw outcomes (.300 slug, .237 wOBA).

In simple terms, Jansen's primary offering was getting crushed, but also getting lucky enough to find gloves or foul ground.

Conclusion

With all the above said, positive regression may hit Jansen's peripherals as much as negative regression might hit his results. If it evens out to an above-average marriage of expected and true outcomes, that's still a plus arm to have in the bullpen.

The D-backs, meanwhile, would do better to get an experienced closer than to bargain-shop. Spending a slightly-higher dollar amount on a closer who knows how to navigate a ninth inning is absolutely worth a decent investment.

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But Jansen would still be a significant risk. Perhaps his good injury luck runs out in his age-38 season. Perhaps his batted ball luck takes a severe turn for the worst.

Even still, it's worth a look. The D-backs can hardly do much worse than their 2025 save conversion rate of 59% from their rag-tag group of journeymen and rookies.