This is incorrect. Baseball Prospectus' replacement level is a replacement level hitter and fielder, position be damned. In other words they're saying that a replacement level shortstop is a .230 EqA hitter who fields over thirty runs below average. Replacement level players are not nearly that bad. In the case of a second baseman their replacement level second baseman is a .230 EqA hitter who fields about thirty runs below average. Even Alfonso Soriano wasn't that bad defensively. It's an incredibly stupid the way they do it, and if you cornered the folks at BP and asked them to defend it, they'd buckle. In reality a replacement level middle infielder will have an EqA between .220 and .230, but can easily defend at an average to above average rate. League average defensive players grow on trees. The distribution of defensive talent is more or less a traditional normal bell curve for the major and upper minor leaguers. The majority of them are in the middle. The distribution of offensive talent isn't the same. It's obviously more or less a traditional bell curve in the majors, but all the players in the minors would tend to fall on the below average side. That's not true on defense.