It's rare for a viable World Series contender to even consider using a rookie as its closer, but the Detroit Tigers did just that entering spring training. After Jose Valverde blew up in the playoffs for the second straight year, the Tigers cut him loose and cast their lot with young Bruce Rondon.
Rondon originally tried out for teams as a catcher before signing with the Tigers out of Venezuela in 2007. In many ways, he's reminiscent of Valverde, as Rondon is huge (6-foot-3, 275 pounds) and relies heavily on his fastball. He introduced himself to a national audience by hitting 102 mph with his first pitch at the 2012 Futures Game, has topped out at 103 mph and usually ranges from 97-100. His heater has good arm-side run, eliciting both swings and misses and broken bats.