BJ Upton made 4.83M last year and should be headed for a fairly significant raise after his best year since his rookie year. The Rays have an in-house cheap replacement in Desmond Jennings to take over and were rumored to have been shopping Upton at the deadline last year.
The Giants could trade Hector Sanchez and Nate Schierholtz for Upton. Schierholtz is the type of cheap, versatile, solid defender the Rays covet. With Jennings in CF, Schierholtz can be a part of a platoon in their LF and RF spots. The Rays only organizational weakness is Catcher, and Hector Sanchez would become their best prospect at the position and one close to taking over in the next two years. The Nationals are also known to like Upton, and they too have a good extra catching prospect in Derek Norris (Wilson Ramos has been rescued). They also have a much deeper farm system than the Giants if it got to a bidding war.
This move pushes Melky Cabrera to RF, and upgrades two spots. It gives the Giants a dynamic RF/CF defensive combo, along with two very talented, motivated 27 year old outfielders heading into free agency. Not for nothing, 27 is generally considered a baseball players peak year. Upton in particular is a dynamic talent who has always seemed on the verge of more. Between his contract year/change of scenery/playing in the same division as his younger brother, there is the potential for an All-Star season from the young CF. Slating in Belt at LF, the Giants could also retain Torres as a do-all 4th OF. Financially this move would only be the difference in salary between Schierholtz and Upton, maybe $4-7M? Cost-wise we lose the value of versatility of Schierholtz and an excellent young Catcher prospect, but that is at least trading from our one organizational strength.
Potential downside? In basketball it's often not good to have too many people on a contract year, because the players gun for their own stats. This doesn't exactly translate perfectly to baseball, but neither Melky or BJ necessarily count "great team player" as one of their strengths. So there's potential that two new firebrands coming to to a recent championship team could upset the clubhouse if the team goals are not first on their mind.
Crawford/Free Agent SS