Major league teams this season must notify the commissioner's office of their starting lineups before they are announced at stadiums. The decision Thursday comes in response to the Supreme Court ruling that has led to more widespread legal gambling.
Through last season, clubs announced lineups as they wanted, some by posting in clubhouses, others in email to media, on Twitter or their websites.
Starting this season, a team must send the starting lineup to Major League Baseball's data operations group 15 minutes in advance of whatever time the club plans to announce it.
MLB will confirm receipt and then distribute the information to its data and business partners. The team may announce the lineup either when it receives confirmation of receipt by MLB or 15 minutes after sending MLB the lineups.
"We are updating a number of our procedures to reduce integrity risks associated with the expansion of sports betting in light of the Supreme Court's ruling last May," the commissioner's office said in a statement.
The Supreme Court invalidated a federal law that barred sports betting in most states.