Nice work. I do however think you are undervaluing the defense of the Sandoval/Uggla/Sanchez combo at 1B/2B/3B.

Sandoval is a career 7.6 UZR/150 at 1B and a career -3.6 UZR/150 at 3B which using posiitonal adjustments translates to +12.4 at 1B. I can understand regressing this due to small sample size but I think taking it all the way down to zero is just too much regression. I would think +4 runs (+.4 WAR) should be conservative enough.

Uggla is a career -2.9 UZR/150 (-.3 WAR) at 2B and I see no reason to project this to decline to -5 UZR/150 (-.5 WAR). I would think Uggla is still at his peak defensively and therefore I would not project any decline.

Sanchez has actually been a better career defender at 3B (+17.9 UZR/150) then his very good defense at 2B (+5.8 UZR/150) but the sample size is much smaller. Since 2B and 3B have the same positional adjustment I think we should just add his 2B sample to his 3B sample to get a more accurate picture of his defense at frankly both positions. If we do this then +17.9 in 1339.2 innings combined with +5.8 in 3984.2 innings results in a weighted average of +8.9 UZR/150. Projecting some decline here might be reasonable so let’s just use your +5 UZR/150 (+.5 WAR).

When we sum these revised projections for defensive WAR contributions we get +.6 WAR above your projection of ZERO WAR.

The above combined with the health risks and defensive risks of the available free agent firstbasemen make Uggla the better option in my mind as long as the trade cost is reasonable.