Burke, Reed... maybe Iguchi.
Mauer barely missed being a rookie, again. (He did, however, have one of the best rookie campaigns ever, as a result, at least if you just look at AB/HR, SLG, OPS, etc.)
McPherson could have an impact when he comes back.
If Chipper Jones dies midseason, a la Daryl Kile, Andy Marte might have a big impact.
Wait... we're talking FANTASY impact, right? If not, I think Reed will help his team the most.
Your wisemen don't know how it feels to be thick as a brick...