How much is a baseball player worth to a team? For the Miami Marlins, outfielder Giancarlo Stanton is worth $325 million over 13 years. The player and the team agreed to that record contract in November. It is the longest contract in MLB history and the most expensive for an American athlete. Stanton, who is 25 years old, led the National League with 37 home runs in 2014 and finished second in the MVP voting.