Intrinsic motivation speaks to motivation that is driven by an interest in a given task for its own merits -- enjoyment for enjoyment's sake. Baseball players maintain varying degrees of intrinsic motivation for the game they presumably love. This is a trait that fans of the game share with the on-field heroes they watch day in and day out.
When intrinsic motivation falters, players can always lean on extrinsic (i.e. outside) motivation. In the case of professional athletes, money is perhaps the most obvious external motivator. In theory, greater input (effort) can result in greater output (statistics), ultimately resulting in greater extrinsic reward (money). The history of modern team sports bears this out, something even casual fans know dearly.
Straddling the line between intrinsic and extrinsic is winning. Winning is the ultimate objective when engaging in competition, and is certainly a part of the game of baseball. However, winning can offer additional motivators in its own right, some of them financial. Yet, as some teams struggle to win, players frequently get distracted or otherwise disinterested in the game, often leading to diminished production. Further, as a team's losses mount, it eventually becomes necessary to plan for the future, substituting regular players for other component parts that may contribute in subsequent seasons. This can have positive and negative implications for fantasy players. Simply, players on competitive teams fare better, while players on struggling teams are frequently worse.