The Arizona Diamondbacks announced they have signed infielder/outfielder Martin Prado to a four-year contract Thursday, one week after they acquired him as part of the haul for outfielder Justin Upton. The deal is worth $40 million, according to a FOX Sports report. Prado, 29, was in his final year of arbitration eligibility and could've become a free agent after the 2013 season. He batted .301 with 10 home runs in 690 plate appearances last season for the Atlanta Braves. He's expected to play third base in Arizona to replace Chris Johnson, who also went to the Braves in the multiplayer swap.