Rookie of the Year?

While working on my hobby, I was going through a book of baseball statistics and noticed something strange. Philadelpha thirdbaseman Scott Rolen won the ROTY in 1997, even though his 130 at bats in 1996 should have made him ineligible. How’d this happen?

“Age is mind over matter; if you don’t mind, it don’t matter.” -Leroy “Satchel” Paige