Even Major League Baseball umpires are adjusting to the new rules.

On opening day Thursday, the umpires called a strike against the New York Mets' Jeff McNeil because of a runner on first.

The umps initially ruled Pete Alonso did not get back to first base in time after a pitch. That put McNeil in an 0-2 hole despite only one pitch being thrown.

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However, manager Buck Showalter said Friday the umps made a mistake, and a strike should not have been called.

Under the new rules, pitchers have 15 seconds to deliver a pitch, 20 with one or more runners on base. Batters have eight seconds to be "alert" in the batter's box.

But the umps admitted to Showalter that a strike should not have been assessed to McNeil, who hit an RBI single anyway.

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Showalter also said umps will start to issue warnings if baserunners are taking their sweet time.

"When I refereed basketball, it’s called preventive officiating, where you go, ‘Hey, get out of the lane,’ instead of blowing the whistle," Showalter said Friday. "If they keep doing it, you pop them." 

The Mets won the game, but fell 2-1 Friday to the Miami Marlins.