Barton had several opportunities to play third base in Sacramento, and they weren't pretty. I personally watched him butcher a ground ball and throw a ball in the dirt to first in the same game a few years ago, and thought "maybe he'll never be a good defender." Obviously I was wrong; Barton is extremely athletic and seemed to pick up the nuances of playing first base relatively quickly.
Daric Barton has been worth positive runs in the field every season he's been the majors, and all that production save one plays has been at first base. Barton went from a catcher with questionable defense to a first baseman with little experience to a very good defender at the position in a span of only a couple years. Barton's fielding value reached its peak to this point at 12.1 RAR this year. The purpose of this post isn't to just blather on and on about Daric Barton's fielding ability at first base, though...it's to think about this: what if the A's had taught Barton to play third base instead?
Part of the reason I assume people would think this idea would fail stems from Barton's previous shoulder injuries, but he seems to have a strong, accurate arm from first base, though he doesn't have to throw nearly as often as he would at third. However, even if we assume that more throwing errors would reduce Barton's fielding RAR by a relatively significant amount, the positional adjustment for 3B was 2.1 RAR in 2010, while the positional adjustment for 1B was -11.4 RAR. First base does have a replacement value of approximately 3.4 RAR more than third base, but in essence this suggests that Barton's defense would have to have been within approximately 10 RAR of what it was at 1B to make his value at 3B worth around the same amount.
Could Daric Barton, with practice, have become essentially a 2 RAR defender at third base? Judging by his athleticism and performance at first base, I don't see why not. This would have allowed the A's to try to fill a hole at first base rather than eventually trade for Kouzmanoff to upgrade the hole at third base, and it's a lot easier to upgrade first base from a WAR of 2.9 than it is to upgrade third base from a WAR of 2.9.
Anyway, my questions to you:
1. Could Barton have successfully become a third baseman?
2. Would the switch have killed his defensive value to the point that it wouldn't have been worth doing?
3. Is this out of the question for the future? Could Barton learn third base on the fly?
It was an interesting thought, and even if I'm way off base, it would've been intriguing to say the least. A 4.9 WAR third baseman would've been sixth in the majors in WAR last year behind only Zimmerman, Beltre, Bautista, Longoria, and Rolen.