It is certainly not much of a drop, I don't have the stats in front of me but i'm pretty certain Walker gets on base at a better clip than Soriano and their defense is probably equal. Walker gets on at a significantly better clip than Soriano and I would argue that his defense is slightly better, though Soriano probably has better range. The power is a drop off, but Walker's isn't bad. Walker also hits for a higher average by quite a fair margin.