Making use of the good ol' Lahman Database I put together a few queries so I could easily compare guys over 2 years. For this I put together a list of every player who had 300+ PA at age 28 and then did the same at age 29 (Bautista had 400 both years, but lets open it up a bit). This gives us 1547 players from 1874/5 to 2008/9. To make sure this stuff works nicely I checked a few other ages traditionally viewed as peak as well. So, what are the peaks and valleys?
Age Year 2 | Avg Jump | Avg Drop | OBP Jump | OBP Drop | Slg Jump | Slg Drop |
25 | 126 | 110 | 160 | 109 | 216 | 238 |
26 | 126 | 143 | 137 | 117 | 234 | 288 |
27 | 111 | 118 | 107 | 105 | 233 | 254 |
28 | 106 | 108 | 128 | 128 | 205 | 220 |
29 | 117 | 115 | 132 | 105 | 250 | 198 |
30 | 126 | 114 | 136 | 134 | 211 | 293 |
31 | 097 | 097 | 123 | 113 | 230 | 288 |
32 | 127 | 106 | 121 | 126 | 315 | 263 |
All Ages | 127 | 143 | 160 | 167 | 315 | 293 |
So, who at age 29 slugged 250 points higher? Canadian Tip O'Neill in 1887. 2nd was Oscar Gamble in 1979 at 223. The other 200+ guy was Tommy Harper at 211 in 1970.
So I have a total of 15,826 paired seasons, out of all of those there has been just one case of someone going beyond a total Slg improvement of 250, that was Javy Lopez in 2003 at the age of 32 vs his age 31 season (372 to 687 with a 169 OPS+, career pre-age 32 was at 478). He followed up with a 503 (127 OPS+) and a 458 (106 OPS+) before finishing with a 386 (75 OPS+ vs his 74 at age 31).
For a 200+ point improvement in slugging we get 23 players all-time including Bautista's current manager Cito Gaston (!) in 1970 at age 26 he jumped by 233 points, 4th best all time. The list, from highest to lowest, is Tip O'Neill, Jeff Bagwell, Cito Gaston, Hugh Duffy, Carl Furillo, Ted Williams (age 41), Oscar Gamble, Lou Gehrig, Gary Carter, Richard Hidalgo, Rico Petrocelli, Andres Galarraga (Colorado), Tommy Harper, Davey Johnson, Bobby Grich, Ralph Kiner, Dusty Baker, Adrian Beltre, Greg Vaughn, George Davis, Mark McGwire, and Fred Lynn. Quite the quality list there with a few odd names mixed in. All of them increase in OBP and Avg as well (no shock) with only Bobby Grich increasing in OBP by less than 40 (only 9 points) and everyone increasing batting average by 43 points or more.
So, what do we see? Guys who jump in Slg% by 200+ points between 2 seasons tend to be very good hitters who also increase in OBP and Slg by over 40 points. Yet Bautista is unique as he will have (most likely) the smallest increase in OBP and Avg outside of Bobby Grich's OBP. Grich slugged 394 lifetime pre his big year, 438 after despite it happening at age 30. His OPS+ pre was 122, 125 after a 145 in the big year (he had a better one 2 years after it). In truth, I'm not sure why Grich's career ended when it did as he had a 109 OPS+ (268/354/412) his final season playing primarily 2B in 1986.
So is he a Cito Gaston type (career year by a landslide), Bobby Grich (stayed at old level but with a bit more power), or Ralph Kiner (stayed at new level)? That is the challenge. Btw, for ISO only Bagwell and Lopez are higher than Bautista with Carlos Beltran (also age 29 but already had done similar) close behind.