[BradG223]

Here's an ugly scatterplot that compares a player's OBP from their first 500 plate-appearances, and the OBP from their final 500 plate-appearances. Players in the green finished with a higher OBP than they started with, and the reverse is true for players in the red.

You don't need to pay too much attention to the ugly mass of points, I'll point out the guys I think are interesting. These are the men with the greatest positive and negative swings.

Dave Bonelli was a two-way player. He is listed as an SP, but he was really an outfielder that could also pitch. For the first 3 years and 1500 at-bats of his career, he had a walk percentage of about 6%. Following his age 24 season, his walk percentage nearly doubled, a key contributor to his rise in OPS.

Kenny Denney (what a name) was drafted in the 7th round and spent 8 years in minor league ball before he finally made his pro debut at age 26. His first year he mostly came off the bench and had a .483 OBP after 176 plate appearances
The following year he squeaked his way into the All-Star Game. After that season he hovered slightly above replacement-level for about 5 years. That was until his final season at age 33, where his decline forced him out of the ABL for good.

I view this as one as a fun experiment, rather than something we gleam meaningful information from.