 Joyner credited a stint with the Mayagüez Indians of the Puerto Rican Professional Baseball League as fundamental in his improvement as a slugger.Then-batting coach José Manuel Morales forced him to do power weight training and modify his posture at the batting cage, so as to develop upper body strength.He was consequently the top hitter on Puerto Rico's winter league on the 1985–86 season, winning the Triple Crown (.356, 14 HR, 48 RBI) in 54 games.