In fact, Zito hasn't helped the Giants much at all since signing a seven-year, $126 million contract in December 2006. The deal has only penned the Giants in, making it hard to keep key players at some times and stifling the team's offseason aggression almost every year.
The deal has become the punch line to dozens of baseball jokes, and the ultimate exemplar of why extreme caution must be taken when signing pitchers to long-term contracts.
Of course, it's not as though Zito was the first or worst mega-deal in the relatively brief history of MLB free agency. Players get overpaid all the time, and some of those deals can hamstring the team who agrees to it, even costing GMs their jobs.
Here are 25 such cases.