Ticket exchange policy

Hello. My brother in law is in town and has never been to an MLB game. My wife bought tickets to the Friday NYY game, but we recently found out Grienke is starting on Saturday. Grienke is my BIL’s favorite player. Does anyone know the exchange policy or if it is possible to change tickets from Fri to Sat? Trying to make this special for someone that hasn’t even flown before. Thanks!