The Case for Bounce Back Performance.
Offense. My view is that offense is what the Diamondbacks need to bounce back most. Can Ketel Marte bounce back from the decline in 2026? Possible reasons follow:
Although this season his bat speed and hard-hit percentages declined (bat speed fell from 85th percentile to 82nd percentile, and hard hit percent fell from 73rd percentile to 64th percentile) those fundamentals remain well above league average. In May and June of this season, his .524 and .558 SLG were above league average. It seems reasonable
that next season, he could reach that level in more than two months.
He is due for a bounce upward in his BABIP. Looking at his seasons with the Diamondbacks, his BABIP was above average in only two seasons (2019 and 2021). Marte’s excellent batting over many seasons was accomplished without the help of above-average BABIP. What if luck goes his way and his BABIP increases?
Over the last ten seasons, each type of pitch thrown has an average BABIP. The following table compares BABIP for Ketel Marte to the league average (each averaged over the last ten seasons). It shows for which types of pitches Marte’s BABIP is better or worse than league average.
In 2026, the biggest changes in pitches thrown to Marte were:
- 3.2% more changeups.
- 3.9% less sliders.
The following table shows this season’s changes in SLG for those two pitch types.
For Sliders, Marte’s SLG fell only a slight amount, perhaps random variation. For changeups, Marte’s SLG fell a lot (from .542 to .290).
My conclusion is that when Marte finds a way to again hit changeups like he did in 2025, that will be a huge part of bouncing back offensively.
His Batting Run Value (Baseball Savant) was 4 in 2026 (about average). It would be reasonable to see this value bounce two thirds back towards his 2025 level, which would be a Batting Run Value of 22 in 2027.
Defense. In 2026, his range fell to a career low of negative 5 (The Fielding Bible). Loss of range is an age-related decline. The bad news is that his range fell, while the good news is that his defense was above average after the fall. Perhaps, he can retain the 2026 level of defensive performance at second base. His 2 DRS and 4 OAA were positive. His Fielding Run Value of 5 (Baseball Savant) was very positive (78th percentile).
Baserunning. Perhaps Marte could mostly avoid stealing (while continuing to take extra bases) to reduce the risk of hamstring reinjury. The consequence would be Baserunning Run Value (Baseball Savant) could fall from 1 in 2026 to 0 in 2027. The upside is that perhaps this allows Marte to play in more games.
The Case for Dwindling Performance
Because Ketel Marte is under contract for four more seasons (albeit with a player option for a fifth season), let’s look at three similar batters in their four seasons after age 32. They are from Baseball Reference’s ‘most similar batters at through [age] 32.’ Their age-32 WARs averaged 2.6, which was similar to Marte’s 2.5 WAR in his age 32 season. The data are shown in the following table:
The similar batters over the next four seasons had 0.725 average WAR. The bad news is that .725 WAR is much less the 2.5 WAR earned in 2026 by Ketel Marte.
Ketel Marte was 33 years old on October 12. He is past his peak and in the decline phase of the aging curve. He is under contract through age-36 (with a player option for age-37), at which time his decline could be significantly large.
“A typical player peaks around age 26 and gradually declines afterward in what we know as the age curve. For those fortunate enough to stick around into their late 30s. that decline becomes quite sharp.” — Roark, October 2021
Last season, Ketel Marte had injuries to his knee and hamstring, which may continue to be nagging problems in future seasons, which could contribute to dwindling performance. Despite my optimism that physical therapists can make improvements that seem like miracles, this could be a significant factor.
As mentioned in the case for bounce back performance, last season his range at second base (The Fielding Bible) was a career low. If instead of having reached the nadir (as assumed in the bounce back scenario), his range could continue to decline, which would contribute to dwindling performance. However, there are limits to the decline because Marte could be moved to designated hitter (DH) to retain his batting performance.
Summary.
Ketel Marte’s performance could improve. Reasons follow:
- His batting fundamentals remain above league averages, while his SLG was above league averages for only two months. That could improve.
- He is due for a bounce upward in his BABIP. His BABIP was above league average for only two of his seasons with the Diamondbacks.
- This season he saw more changeups. Although his SLG for changeups fell by almost half, it is likely he can find a way to improve his performance against changeups.
- If his batting run value bounced toward his level of 2025, his batting run value would be at a high percentile.
- Despite his decline in fielding range, his defense was above-average and it could continue to be above average.
Ketel Marte’s performance could dwindle. Reasons follow:
- Three similar batters, with similar age-32 WARs, showed big declines in age 32 to 36 seasons.
- Ketel Marte was 33 years old on October 12. He is past his peak and in the decline phase of the aging curve. He is under contract through age-36 with a player option for age-37, at which time his decline could be significantly large.
- Last season, Ketel Marte had injuries to his knee and hamstring, which may continue to be nagging problems in future seasons, which could contribute to dwindling performance.
- His range could continue to decline like it did last season. There are limits to the decline because Marte could be moved to DH to retain his batting performance.
