90% of fielders can make 90% of plays at any position because most plays are routine.

If I restricted that to fielders at specific positions, most people would probably agree.  90% of shortstops would make 90% of plays at shortstop.  But what I'm say is that, with two caveats, 90% of fielders can make 90% of plays even if their position is assigned randomly.  The point is that most plays are routine.

The two caveats:
- exclude the positions of pitcher and catcher
- allow for handedness, i.e., do not put lefties at second, third or short.

Then pull names out of a hat and send them out there to play.  I have no data to support this.  It is basically a philosophical assertion.  It is intended to emphasise the idea that fielding is overvalued.  Many, maybe most, plays in a Major Baseball League (MBL) game can be made by competent amateurs.  For MBL players, that should increase to a very high percentage, maybe as high as 90%.

OK, now stop being anal and quibbling about the 90% thing. Consider the Willie Mays factor.  I choose Mays because he is the best example I have for a player being both a really great hitter and a really great fielder.  Substitute your own but follow the point.

In a nine inning game Willie Mays will probably bat four times for the Giants.  He will play center field, which will make it difficult for opposing batters to avoid hitting a ball to him, although that is possible.  In all four of his plate appearances (PA) Mays needs all his skill.  But for how many of his fielding chances does Mays need all his skill?  In many, if not most games, the fielding skill of Willie Mays is not needed.  Any competent MBL center fielder can make the plays.  Probably any competent MBL corner outfielder can make the plays.  In at least some games, any competent MBL player of any position can make the plays.  And in a few games, any competent amatuer can make the plays.

But at the plate, the Giants need Willie Mays in every PA of every game.  Every Willie Mays PA is a potential home run.  But only some of his fielding chances can really save a run and maybe none in a given game.

That's why I think fielding is overvalued.