For years, the primary difference between baseball’s two leagues has been the presence (or absence) of a designated hitter who stands in for the typically offensively-challenged pitcher at the plate. But after St. Louis Cardinals ace Adam Wainwright sustained a season-ending Achilles injury attempting to run out a pop-up in his fourth start of the season, plenty of baseball fans have found themselves asking: Should we still let pitchers hit?

While many would love the National League to adopt the designated hitter and take bats out of pitchers’ hands, purists have argued otherwise, insisting that pitchers—just like all the rest of the defenders—should be responsible for their own offensive output. But why does this discrepancy between leagues exist at all? How did it end up that, in the same sport, one league uses a designated hitter and the other one doesn’t?

Legendary Philadelphia Athletics manager Connie Mack—of the National League, in fact—floated the idea of a designated hitter as early as 1906, lamenting pitchers’ inability to hit. But his attempt, as well as NL President John Heydler’s crusade in 1928, never made it past infancy, according to MLB.com’s Anna Floch. Years passed before the thought of a 10th player in the lineup gained serious traction.

It was the offensively deficient 1960s—a pitching-dominant decade that also necessitated a lowering of the mound as a means to increase offense—that prompted idiosyncratic Oakland A’s owner Charlie O. Finley to crusade for the designated hitter (a crusade that made it into the first sentence of his New York Times obituary). Finley noticed American League attendance lagging behind the National League, and decided something had to be done.

It was an era in which the two leagues operated autonomously from each other and Major League Baseball. The circuits functioned as separate business entities and did not merge under the umbrella of the MLB Commissioner’s office until 2000, meaning their competitiveness was more than just show.

On January 11, 1973, Finley got his wish. AL owners voted 8-4 in favor of a temporary installment of the designated hitter to see if peppier offense could boost ticket sales. It was couched as a “designated pinch-hitter” to be substituted for the pitcher at the plate in clutch situations, and it had already been experimented with for a few years in the Minor Leagues. This marked the first time since the inception of the American League in 1901 that the two leagues operated under different rules.

National League President Charles S. Feeney offered straightforward rationale to The New York Times’ Joseph Durso after his league voted against the rule change: "We like the game the way it is." MLB commissioner Bowie Kuhn chimed in, telling the Times, "I hope it works. I would have preferred that both leagues did it. But if it's successful in one, then I hope the National follows suit."

It did work—the American League’s three-year experiment became a mainstay, one that remained unique to the AL through the leagues’ merger 27 years later. However, contrary to Kuhn’s wishes, the National League has yet to follow suit. But now, 31 years after Kuhn’s retirement and eight years after his death, his wishes are seemingly closer than ever to coming true.