虽然很多人很气
觉得裁判乱判
但是根据大联盟的rule book
definition of terms
A FAIR BALL is a batted ball that settles on fair ground between home and first
base, or between home and third base, or that is on or over fair territory when
bounding to the outfield past first or third base, or that
touches first, second or third base, or that first falls on fair territory on or
beyond first base or third base, or that, while on or over fair territory touch
es the person of an umpire or player, or that, while over fair territory, passes
out of the playing field in flight.
太长我直接抓重点
“while on or over fair territory touches the person of an umpire or player”
线本身包含在fair territory里
当防守球员碰到球的瞬间，球"on"或者是"over" fair territory，就算fair ball
所以即使球本身没有on在线上，只是over在线的上空也算界内区
Official Baseball Rules
2026 Edition
p.151