Related Clues:

• Call balls, say
• Worker behind the plate
• Sport authority
• Duster at home, sometimes
• Bag man?
• Official in black
• Official behind a catcher
• Diamond ref
• Man in blue, often
• Authority behind home
• Ref's colleague
• Masked one at home
• Oft-booed official
• Expert on a 68-Across
• Baseball arbiter, for short