According to baseball historian John Thorn, 1839 is the year Adams became a baseball player. In an 1896 interview in The Sporting News, Adams said that “soon after going to New York I began to play base ball just for exercise, with a number of other young medical men.” Starting in 1840, he was a player with the New York Base Ball Club. This team had been founded in 1837, eight years earlier than the New York Knickerbockers, who are credited in several baseball histories as pioneering the modern version of baseball. Adams played an early form of the game, but Thorn writes that he “understood [it] to be baseball, no matter what it was called”.

Doc Adams, Wikipedia

Adams received an invitation to become a member of the Knickerbockers a month or so after the team’s September 23, 1845, creation. He accepted and joined the club along with other men in the medical field; he later said that players from the New York Base Ball Club were behind the formation of the Knickerbockers. Records of the club’s practice games indicate that he was a member of the Knickerbockers by November 18, 1845. In an inter-squad game held that day, which was the Knickerbockers’ last of the year, Adams scored nine runs for his team as they defeated a side picked by William R. Wheaton, 51–42. The club organized its first game against outside opposition in 1846; at a June 5 meeting Adams was selected to a three-man committee whose aim was to set up a game against the New York Base Ball Club. The committee’s efforts were successful, and a game was scheduled on June 19. Adams participated in the contest, which the Knickerbockers lost 23–1. Batting second in the Knickerbockers’ lineup, he made one out and did not score a run.

Doc Adams, Wikipedia