I agree with Spitball, of the 8 playoff teams, the lowest OPS+ was 102 for the starting 1st baseman and the average of all eight was 124. While it's true that you can pretty much get anyone to play first base, it seems like having "just anyone" and an "elite level" first baseman may be the difference between playoffs and not. (For my survey I used Cuddyer for the Twins because he logged the most at bats, and Moreland for the Rangers because Smoak was traded away.)

Player OPS
Pena 102
Texeira 125
Cuddyer 104
Moreland 123
Howard 128
Votto 174
Glauss 102
Huff 138
Average 124.5