The bottom line is they have gotten awful hitting from 1B and LF, generally the 2 easiest positions to get decent offense from, and 3B, less easy but still typically counted on for run production. If they can turn those spots in the order from huge minuses to pluses or at least something approaching decent, and find 2-3 more good relievers in addition to Qualls, Fields, Sipp and whoever else (Folty, or will he start next year?), then it's not hard to picture this team being decent.
Of course, one could question whether Keuchel and McHugh will be able to replicate their excellent numbers next year, but all in all the rotation looks to be in decent shape.
FWIW, I hope they keep Fowler too (and bat him leadoff, where he belongs, for God's sake).