Buster Posey has less than a year’s worth of service time, so he has zero leverage. If the Giants wanted to, then, they could pay him $417, 000 which is the MLB minimum. His Rookie of the Year season has earned him a slight bump, however, as the Giants have decided to give him $575,000 according to Hank Schulman of the Chronicle.
That’s just how things work for a guy who hasn’t reached arbitration eligibility. And it’s also why, when a good player gets a big contract later, it’s a little misguided to say that he’s overpaid. Because for the guys like Posey who make big splashes early, they spend three years being significantly underpaid.