When it comes to crossover athletes, there are enduring legends like Bo Jackson and Deion Sanders, and then there are more marginals cases like Brian Jordan and Drew Henson. Baseball is incredibly time-consuming, from a 162-game regular season in the MLB down to travel teams in top-flight youth baseball, so it allows precious little time for other endeavors, let alone another professional sport, but at least it's low-impact.
While few of these players participated in their crossover sport beyond the high school level, it's a testament to the tremendous athletic ability possessed by the average baseball player (David Ortiz notwithstanding).