Little Big League (1994)

When the owner of the Minnesota Twins dies suddenly, his will bequeaths the team to his grandson, Billy, a devotee of baseball who, although he's only 12, has devoured voluminous lore, knows them intimately, and has shown an uncanny sixth sense of what they need to improve. They hate their manager, so Billy quickly fires the SOB, winning their instant approval. However, this turns to dismay when he announces their new manager: Billy. How will he convince a gang of proud, tough men to stick around and take orders from a kid? On the other hand, what's to lose-- they have nowhere to go but up.