Made judgments on diamonds

• Helped out at a T-ball game, perhaps
• Officiated at T-ball
• Called strikes, say
• Called a ballgame
• Refereed, briefly
• Called the game
• Called out?
• Made lots of calls, in a way
• Officiated on the court

Wiktionary Word definitions in Wiktionary
vb. (en-past of: ump)