The quotation suggests Cory's belief that racism was the hurdle preventing his father's major-league baseball success, reflecting broader social issues of racial exclusion in sports historically.
The inference most strongly supported by the scene in which Troy and Cory discuss baseball is that Cory believes that his father would have been a successful major-league player if it wasn’t for racism. The conversation implies a recognition of the racial barriers that existed in the past, and the belief in Troy's potential.
Furthermore, this belief is anchored by the historical context; black players, for a long time, were excluded from major league sports due to racial biases. Yet, the narrative also reflects how local passion for sport and exceptional talent can break through barriers, as seen with the Kansas City Call's portrayal of the impact of the Monarchs and the eventual breaking of the color line with Jackie Robinson's entry into the Major Leagues.