how will it work?
1 The manager comes onto the field and announces he is challenging an umpire's call (no, there is not a red flag involved).
2 The crew chief, using an on-field headset, contacts the replay command center in New York, which will be staffed by umpires.
3 After viewing video feeds, a replay official decides whether to uphold or overturn the call. The decision goes back to the umpire.
What's reviewable?
• Home run
• Ground-rule double
• Fan interference
• Stadium boundary calls (e.g., fielder into stands, ball into stands triggering dead ball)
• Force play