Concerned by game times that have bloated beyond three hours, Major League Baseball is putting baseball on a diet for the 2015 season. In upcoming games, timers will regulate the pause between innings, and hitters must now keep one foot in the batter's box nearly all the time.

"The most fundamental starting point for improving the pace of the average game involves getting into and out of breaks seamlessly," Commissioner Rob Manfred said of the new rules that were announced Friday.

"In addition, the batter's box rule will help speed up a basic action of the game," he said.

Exceptions to the new rules will be allowed, particularly for pitchers who batted or were on base in the previous inning. For hitters, they'll be allowed to move out the batter's box if they swing at a pitch, among other situations.

Other changes address instant replay, which was blamed for prolonging games last season, particularly as team managers strolled toward an umpire as their team considered challenging an on-field decision. For 2015, managers can both hold play and file a challenge from the top step of the dugout.

The new changes mean that fans can expect to see new clocks ticking down the seconds in MLB stadiums this season — with one timer mandated in the area of the outfield scoreboard, and another for the area around the press box behind home plate.

But they're not the "pitch clocks" many in the game had dreaded. The clocks are only meant to shorten the gap in the action between innings.

"Immediately following the third out of each half-inning, the timer will count down from 2:25 for locally televised games and from 2:45 for nationally televised games," the league says.

Here's a rundown of the times MLB will allot and track after the return from a between-innings break:

The league says the rules "will be enforced through a warning and fine system, with discipline resulting for flagrant violators."

It remains to be seen how players who are famous for performing painstaking and time-consuming home plate rituals, such as the San Francisco Giants' Pablo Sandoval, might adjust their habits. (Sandoval has discussed his ritual in the past.)

Atlanta Braves executive John Schuerholz, who heads MLB's Pace of Game and Instant Replay committees, says the changes weren't made "to achieve a dramatic time reduction right away" but instead "to develop a culture of better habits and a structure with more exact timings for non-game action."

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