Potential D-backs Free Agency Target: Kenley Jansen

The future hall of fame closer could make his way to Phoenix this winter.

Aug 17, 2024; Baltimore, Maryland, USA; Boston Red Sox pitcher Kenley Jansen (74) reacts after finishing the game between the Baltimore Orioles and the Boston Red Sox at Oriole Park at Camden Yards. Mandatory Credit: Reggie Hildred-Imagn Images / Reggie Hildred-Imagn Images

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

Kenley Jansen, Closer, 37 years old

One of the greatest relievers of a generation, Kenley Jansen is once again on the market. His cutter has dominated big leaguers for 15 seasons now, helping him to what is likely a hall-of-fame-worthy career. Now at 37 years old, the Diamondbacks could be among the teams bidding for his services.

Arizona has had a busy winter. They made a massive splash, signing Corbin Burnes to a monumental 6-year 210 million dollar deal. They have also traded for 2024 All-Star Josh Naylor and re-signed Randal Grichuk. Still, a hole in the bullpen remains and is now a prime target for D-backs GM Mike Hazen. Could Jansen fill that role?

Pros

Experience

When it comes to premier closer experience there aren't many players with more than Kenley Jansen. 15 years in the big leagues entering 2025 and 4th on the all-time saves leaderboard, it seems like he wants to keep it going.

The Diamondbacks could use someone with Jansen's reputation in a 9th inning role, particularily due to their youthful bullpen. Names like Justin Martinez and Drey Jameson will be staples of the Arizona relief core for years to come, but while they find their footing in the big leagues, bringing in an arm with 447 career saves would certainly make an impact.

Pitching+

Pitching+ is one of three models developed by Reno Sarris and Max Bay. They created it in an effort to look at the process underlying a pitcher’s performance. This removes some of the noise included in the on field results that a pitcher provides and helps give a better picture of how good a pitcher truly is.

When looking at Pitching+ leaderboards familiar names headline the rankings, but among the best in baseball, even at 37 years old, is Kenley Jansen. Coming in at a fantastic 115 Pitching+, or 15% above league average, Jansen still holds one of the best overall pitching processes in baseball.

According to Sarris, Pitching+ from the year prior "out-predicts any current projection system for relievers when judged by the size of the Root Mean Square Error".

Below is a list of oft mentioned relievers that could be potential targets for the Diamondbacks. This ranking lands him just below elite closers Ryan Helsley and Mason Miller, and above names like Pete Fairbanks and other hall of fame candidate Craig Kimbrel.

Diamondbacks reliever acquisition candidates ranked by Pitching+ / Jack Sommers

While these numbers can't precisely predict future results, these favorable views, along with a far better 3.00 FIP compared to a 3.29 ERA in 2024 point to Jansen as a great pitcher and a potential rebound candidate.

Cons

Age

When praising Jansen for his experience one must also point out that this wealth of knowledge may also come at a cost. Age is a concern for every player and general manager alike. It is unpredictable and affects every player differently. Still, regression is always a real concern.

Being 37 years old comes with a price on your body, and while the right hander hasn't been hit by father time yet, it can never be ruled out that a falloff is right around the corner. His velocity on his elite cutter has stayed relatively the same, with some minor fluctuation but relative consistency, and his health to this point hasn't been a massice concern.

Still, the Diamondbacks have quite a lot of experience with aging veterans entering the twilights of their career as soon as they pass through Chase Field's gates. This is obviously something the club would like to avoid if at all possible.

Flexibility

Acquiring an arm like Kenley Jansen does come with role based expectations. As a premier closer over nearly two decades, he has become quite comfortable in that position. The D-backs, while lacking a clear 9th inning man, do have up and coming talent vying for this spot.

Justin Martinez is the clearest case of this. While still young and improving he's demonstrated incredible talent and has seen impressive development in his command throughout the last two seasons. If the team were to make a call and switch Jansen out of a 9th inning role, it would be important to avoid any personal hardship in the process.

Conclusion

Kenley Jansen is a legendary talent in the game of baseball. He has displayed a mastery of his craft throughout the last 15 years and would be a perfect theoretical fit for a team missing an experienced closer.

Impressively he ranks among the best in baseball in terms of Pitching+ and even his underlying metrics suggest room for positive regression. Still, age, flexibility, and fear of health issues could dissuade the Diamondbacks from pursuing a deal with the veteran right-hander.

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