If Rafaela is higher, it’s presumably due to Casas being a 1b, not exactly a position many teams struggle to fill and it’s the position more players switch to than any other. As some scouts rank not ability, but likelihood of being an impact player, the competition at 1b should impact the ranking. Doesn’t mean Casas is worse than Rafaela. Just means he plays a tougher role.
Bear in mind reigning NL MVP Paul Goldschmidt, who also has three other top 3 MVP finishes, was never ranked by anyone in any top 100, despite absolutely raking throughout his entire minor league career. 1b is a tough position to get ranked sometimes…