Long before the NFL, NBA, NHL and MLB secured reigns of dominance over their respective sporting realms, these titans had to deal with upstart sports leagues vying for a piece of the Iron Throne. Stealing top draft prospects, siphoning away veterans and in some cases securing lucrative television deals, these alternate leagues had a profound impact on the development of their separate sports.

Whether through merger or phase-out, all of these alternative leagues eventually went out of business. The retirement of the last players to have played in both the alternative and the dominant leagues marks the end of an era. Here are these players and a look inside the leagues that helped shape professional sports into what they are today.

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