OPP+ is simply OPP adjusted to the league average. It does not account for ballpark effects. It can be calculated very simply:

OPP+ = (OPP / League OPP) * 100.

A 100 OPP+ is average. The amount above or below 100 is equal to the percentage above or below the league average, so a 108 OPP+ is equal to an OPP 8% above league average, while an OPP+ of 87 is equal to 13% below league average.

Since we are dealing with multiple seasons here, I used the league average OPP for all seasons in which a player appeared. This may not be strictly the same as the actual league average OPP for the player’s career, but it will be very close.

Stats go back to 1950. Player links go to Baseball-Reference.

Career OPP+ Leaders (6000+ PA)

Compared to the standard career OPP Leaderboard,

old-school players fared quite a bit better, and the more recent players fared a bit worse. There are still quite a few active players on the list (9, in fact). These players will likely see drops in their OPP+ as they enter/continue their decline phases. We may also be seeing more recent players due to the increased emphasis on getting on base that some front offices have used since the mid-1990s.

By the way, the next 3 players who missed the cutoff for this list were all active as well: Alex Rodriguez, Derek Jeter, and Adam Dunn (all at an OPP+ of 117).