In real life, if you buy a product that doesn't do what it's supposed to, you can return it. If you purchase a blender that doesn't mix food, or a lawnmower that doesn't cut grass, you can usually get a refund or exchange it for one that works.
Baseball teams don't have that luxury. When GMs sign players, the name of the game is caveat emptor—buyer beware.
If a team signs a player expecting him to contribute 15 wins or 30 homers a year and he doesn't deliver, there's no way to return him for store credit, and he still gets paid like a star.
The following are the 10 players who have given their respective teams the worst returns on their hefty investments this season. Some have been merely disappointing, some have been used inefficiently, and some have actually been worse than a replacement-level scrub.
To help illustrate just how overpaid these players are, each slide contains the player's FanGraphs Salary Valuation (an estimate of how much a player's production is worth, based on Wins Above Replacement) for the 2010 season, projected over 162 games. Some of them have been so bad that they've actually provided their teams with negative value.
Congratulations to the teams whose players aren't on this list!
Thanks to Cot's Baseball Contracts for the salary figures.