By acquiring Jack Wilson, Seattle is acting a bit like a buyer, although the Mariners didn't touch their top tier of prospects to add Wilson and Ian Snell. The Pirates, meanwhile, trade two players with limited markets to add some pitching depth to their system.I imagine Seattle's motivation for acquiring Wilson and apparently picking up his $8.4 million option for 2010 is based on his defensive value; Wilson is one of the best defensive shortstops in the majors, ranking at or near the top of National League shortstops in every advanced defensive metric this season. Wilson is, of course, a terrible offensive player, and he's not going to be any less terrible in the better league. He also is 31 and has lost what speed he once had, so his defensive abilities are much more likely to decline in the future than they are to improve or even stay at this level. Seattle has made strides in the standings this season by emphasizing defense, but the thing about loving defense and finding it to be an undervalued asset is that if you pay Wilson $8.4 million, it's not an undervalued asset anymore.