1952 Slaughter was 6-for-7 in stolen bases for the entire season in real life (618 PA/162) and has 66 speed.

I just finished a league where he stole 85 bases against 15 CS. 

No one else on his team went nuts. Frankie Frisch '34 (RL 11/23) didn't even attempt a steal. Terry Moore '35 (RL 13/22) stole 16 bases and was caught 6 times. So it's not like they played in a division full of Piazzas. 

His owner didn't play in any live games. I checked Slaughter's game log and he doesn't have any 20-steal games or anything nuts like that. The most he stole in 1 game was 3 bases.

How in the world does that happen? Has anyone else seen anything like this before?

Try this link:  http://whatifsports.com/mlb-l/playerstats.asp?teamid=1113722&ltid=0&lid=99426 

That's probably it.

I had something like that recently. I accidentally left a Rusty Staub off my progressive roster. Halfway through the season I realized it and had admin add him back on in place of a junky relief pitcher. Staub showed up the rest of the season with the relief pitcher's stats.

That's right... I forgot about that. He replaced Brock, and took over Brock's stats. Thanks everyone.