Is it my imagination, or are there quite a few very good options among 3B? Besides Schmidt and Brett, you got Harrah, Cey, Oberkfell, Horner, Lansford, Madlock, Molitor, DeCinces, Gaetti, Bell, Boggs and Wallach. I mean, I know other positions have some depth, but this is a VERY good pool. There are a variety of player types: power monger/hoovers [Schmidt, DeCinces, Gaetti], contact hitters [Bell, Oberkfell, Madlock, Boggs, Brett [a line drive hitter, really]), speedy types [harrah, molitor, Lansford [and madlock again]); slow pokers with power [horner, cey]), speed/power in the right years [harrah, molitor, and Gruber, who's not on this list).
Speaking of Gruber, the secondary list of players has him, Nettles, Knight, Brooks, Larrry Parrish. Lots of choices at 3B, it seems, any of whom can give you something.
So, what's the thinnest pool? Shortstop? What is there but a crap shoot after Yount (no unusable cards), Trammell (1 poor year, relatively speaking), Smith (not much of a hitter, but walks and SB's), Fernandez (one not so good year, but he's a 1), Ripken (a poor year and a skewed year), and Larkin (one baaaaad year)? What comes after that? Templeton, Concepcion, Bowa, Smalley?
What about catcher? To me, there's more to like than at SS. But I'll leave this to others.