Rusney Castillo

After he signed in August 2014, Castillo, who hadn't played in a competitive situation since 2013, hinted at his potential in 120 plate appearances at various levels of the organization before a thumb injury cut short his winter offseason. Castillo didn't transition to baseball in the States as quickly as a seven-year, $72.5 million contract suggested it would. He had an oblique injury in spring training and didn't get enough at-bats, so it was off to Triple-A Pawtucket where he endured a few more minor injuries before getting a callup in May. Major league pitchers were able to exploit his aggressiveness at the plate and there were questions about his baseball IQ. He eventually got regular playing time and played well, but again not as much as his big contract would suggest. He's expected to open the season as a starter, probably in left field, but could lose out on at-bats against left-handed pitching to Chris Young.

Castillo is a bit of mystery. The Red Sox out-bid several other teams and signed him to a six-year, $72 million deal in late August. His initial assignment in Boston's minor-league system was his first competitive baseball in 18 months. After some time at Boston's various minor-league affiliates, Castillo made 40 plate appearances (10 games) for Boston late in September and began to flash his potential in the final week of the season, going 8-for-16 with six runs, three walks, two stolen bases, two homers and five RBI in his final five games. The plan called for him to get 200 plate appearances, including his work in the minors, majors, Arizona Fall League and Puerto Rican winter ball before shutting down. He suffered a bruised hand in the Fall League, but it was a minor injury, and he eventually reported to Puerto Rico to finish off his offseason program. Scouts say he's a five-tool player, and the team's investment in him points to a significant long-term role. An oblique injury during spring training and a crowded depth chart prompted the Red Sox to option Castillo to Triple-A to begin the year, while Mookie Betts is positioned as the team's starting center fielder for Opening Day. Castillo may only be a Shane Victorino injury away from getting a regular spot in Boston.