The Evidence
The verdict is NOT YET. The six signals behind it are on the verdict page and his path against both groups is on Progression. This page asks the question underneath both: what actually separated the two groups.
What separated them
The groups did not differ by luck. They differed by the same traits the scorecard tracks, which is why those six are the six.
Lasted
Elite exit velocity, power to all fields, controlled strikeouts, and they stayed on the field. At 31, none of them showed erosion in any of it.
- Nelson Cruz147 OPS+ across ages 33 to 40
- David Ortiz163 OPS+ at 40: .315/.401/.620 with 38 home runs
- Paul Konerko39 home runs and a .312 average at 34
- Frank Thomas39 home runs and a 139 OPS+ at 38
- Edgar Martinez141 OPS+ or better every year from 35 through 40, with 37 home runs at 37
- Jim Thome42 home runs at 35, then 35 and 34 in the two seasons after
- Fred McGriff30 home runs and a 125 OPS+ at 38, his tenth and last 30-homer season
Collapsed
Pull-only power with no fallback, rising whiffs, or an injury cascade. The erosion was visible by 31.
- Ryan HowardA 123 OPS+ at 31, then the Achilles tore on the last play of that October and he topped out at 111 across five more seasons
- Chris DavisA 46 OPS+ at 32, two years after signing for seven years and $161M
- Mark TeixeiraStill a 143 OPS+ at 35 but only 111 games, then 76 at 36 and done
- Jose Abreu137 OPS+ at 35, then 87 at 36 and .124 at 37
- Edwin EncarnacionPull-heavy exception: 34 home runs and a 130 OPS+ at 36, then 68 at 37
- Prince FielderRan a 547-game streak, then two neck surgeries 26 months apart ended his career at 32
- Adrian GonzalezA 128 OPS+ at 33, then 69 at 35 and out of the league at 36
Where Alonso sitsHe matches the hitters who lasted on five of six signals. The exception is strikeout rate.
Fourteen players, seven per group, chosen to illustrate two archetypes rather than sampled at random. That selection makes the two paths look more distinct than the full population would, and it is the largest caveat on this page.
Where every line above comes from
Ages follow the Baseball-Reference convention, age as of 30 June. Two of these facts were wrong when this page first shipped, and they lasted as long as they did because nothing recorded where they came from. Each one is now checkable.
- Nelson Cruz
- StatMuse season tables, 2014 to 2021: 138, 158, 148, 147, 133, 164, 166, 123
- David Ortiz
- StatMuse season table, 2016
- Paul Konerko
- StatMuse season table, 2010. His career high of 41 came at 28, not at 34.
- Frank Thomas
- StatMuse season table, 2006: .270/.381/.545
- Edgar Martinez
- StatMuse season tables, 1998 to 2003: 157, 161, 154, 157, 141, 143
- Jim Thome
- StatMuse season tables, 2006 to 2008
- Fred McGriff
- StatMuse and contemporaneous reporting, 2002 Cubs: .273/.353/.505
- Ryan Howard
- StatMuse season tables, 2011 to 2016. The Achilles went on the final out of the 2011 NLDS, in his age-31 season, not at 32.
- Chris Davis
- StatMuse season tables, 2016 to 2020; contract signed January 2016
- Mark Teixeira
- StatMuse season tables, 2013 to 2016
- Jose Abreu
- StatMuse season tables, 2022 to 2024
- Edwin Encarnacion
- StatMuse season tables, 2018 to 2020
- Prince Fielder
- Fox Sports, streak ended at 547 games in May 2014; ESPN, second cervical fusion July 2016 after which he was not cleared to play
- Adrian Gonzalez
- StatMuse season tables, 2015 to 2018. Ages recomputed from his 8 May 1982 birthdate; StatMuse labelled these seasons two years older than they were.
The counterexampleDurability lowers cliff risk but cannot erase it. Prince Fielder ran a 547-game streak, longer than Alonso’s, and two neck surgeries 26 months apart ended his career at 32.
The bottom line
No measurable decline yet at 31.
The early-warning indicators are a sustained strikeout climb toward 28 to 30 percent, or average exit velocity under 92 mph.
If those stay clean, expect a productive window through 33 and a fade at 34 to 35. That is a projection, not a promise, and this site will say so when it changes.