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

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

The umpires initially ruled that Pete Alonso did not return 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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New York Mets manager Buck Showalter talks with home plate umpire Paul Emmel about a call during the seventh inning against the Miami Marlins on June 24, 2022 in Miami, Florida. (Eric Espada/Getty Images)

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

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

But the umpires conceded to Showalter that a strike should not have been called for McNeil, who hit an RBI single anyway.

Pete Alonso of the New York Mets walks the bases after hitting a home run against the Miami Marlins during the ninth inning at LoanDepot Park on March 31, 2023 in Miami, Florida.

Pete Alonso of the New York Mets walks the bases after hitting a home run against the Miami Marlins during the ninth inning at LoanDepot Park on March 31, 2023 in Miami, Florida. (Megan Briggs/Getty Images)

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Showalter also said umpires will start issuing warnings if baserunners are taking their time.

«When I referee basketball, it’s called preemptive officiating, where you say, ‘Hey, get out of the lane,’ instead of blowing the whistle,» Showalter said Friday. «If they keep doing it, you blow them up.»

New York Mets manager Buck Showalter discusses a call with referee Larry Vanover during a game against the Washington Nationals at Nationals Park on August 1, 2022 in Washington, DC

New York Mets manager Buck Showalter discusses a call with referee Larry Vanover during a game against the Washington Nationals at Nationals Park on August 1, 2022 in Washington, DC (Mitchell Layton/Getty Images)

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