Yanks pick up Sheff's option

Three possible explanations:

1) Since the Yanks know it's an inflated market, Sheff at 13 million for just one year is a great option. They actually intentend to play him at first, despite the fact that he doesn't want to.

2) They know Sheffield will demand a trade in which the other team signs him to a contract extension. This way, they at least get something back for Sheff, as to before when they would only get a compensatory draft pick (he might only be a B player since he barely played in 06).

3) They'll sign Sheff to an extension and keep him, and now they have exclusive negotiating rights.