Major League Baseball will require teams to start many games earlier than normal beginning in 2018, thanks to a provision in the new labor agreement that goes into effect when either team faces a flight longer than 2½ hours after the game.

Sources told ESPN that the getaway-day changes will apply if a team has a game -- or even an off day at home -- the next day.

The new rules also will prohibit teams from scheduling an early-afternoon game the following day if one of the clubs played a night game in a different city the evening before.

The changes were adopted after the players' union made scheduling and start times a priority in the labor talks, in an effort to reduce the wear and tear of travel and sleep deprivation.

Players have long complained about the number of trips that force teams to arrive at their next destination at 5 a.m. local time or later, allowing for just a few hours of sleep before it's time to go to the ballpark.

In an interview with ESPN last month, union chief Tony Clark said the new rules were "fundamental to the health and performance" of players and were negotiated "against the backdrop of keeping guys on the field as often as possible."

On June 9 of this past season, the Los Angeles Angels played a night game in New York that started at about 7 p.m. ET. They then played a night game at home the next day. Under the new rules, their getaway-day game in New York would not be allowed to start later than 4:37 p.m. ET.

Another example would have affected the much-discussed Aug. 17-18 schedule of the Boston Red Sox, who played a Wednesday night game in Baltimore and then had a Thursday afternoon game in Detroit that started at 1:10 p.m.

Under the new rules, the Orioles would not have been required to move up their 7 p.m. start time because the Red Sox did not face a flight of more than 2½ hours. However, the Tigers would not have been allowed to start their game the next day earlier than 5 p.m.

The agreement allows for certain special exceptions involving holidays and trips to Wrigley Field, where local laws provide less flexibility in scheduling later start times. However, even those exceptions are restricted to instances in which teams face shorter flights.