This paper describes the forms of knowledge used by players of fantasy sports, games where players create ideal sports teams and compete to accumulate points based on professional athletes' statistical performances. Messages from a discussion forum associated with a popular fantasy basketball game were analyzed to understand how players described their decision-making strategies to their peers. The focus of the research was to understand if players use mathematical concepts such as optimization and statistical analyses when assembling their team or if they base their decisions on personal preferences, beliefs, and biases. The analyses in this paper suggest the latter, that players rely on informal, domain-specific heuristics that often lead to the creation of competitive teams. These heuristics and other forms of player discourse related to knowledge use are described. The paper also suggests ways that analyses of existing practices might provide a foundation for creating gaming environments that assist the acquisition of more formal reasoning skills.