SAN FRANCISCO — Giants first baseman Rafael Devers apologized to manager Tony Vitello and said his actions at first base in the ninth inning of San Francisco’s one-run loss to the Miami Marlins on Sunday are being “blown out of proportion.”

Vitello backed his player, calling it a “nonissue.”

After drawing a leadoff walk Sunday in Miami, Devers waved off pinch runner Jonah Cox and gestured angrily toward the dugout when the rookie came out. When first-base umpire Nate Tomlinson made the substitution official, Devers covered his face with his helmet and yelled into it. Upon reaching the dugout, he avoided a backslap from bench coach Jayce Tingler and headed directly for the clubhouse.

Devers, who rarely speaks to the media, did not speak to reporters after Sunday’s game. On Tuesday, before the Giants played the Athletics at Oracle Park, Devers said the confusion arose because he believed Vitello was removing him from the game because of a lingering hamstring issue, which he said is no longer a problem.

“I think it was a misunderstanding,” Devers said through an interpreter. “I thought the hamstring was the reason he was taking me out of the game.”

Cox, a rookie with less than a month of big league experience, is one of the faster players in the majors. He did not attempt to steal second base, and the game ended when Willy Adames hit into a double play.

The loss completed a three-game sweep for the Marlins and dropped the Giants to 15 games under .500, the second-worst record in the National League.

Buster Posey, the Giants’ vice president of baseball operations, said Tuesday, “We’re all prone to have missteps at times.”

Posey said he had not spoken to Devers, but added, “You could tell he’s frustrated. Look, the way the season’s gone, everybody’s frustrated.”

Devers said he apologized to Vitello — “It was the right thing to do,” he said — in the manager’s office in Miami after the game. Vitello said the conversation took place when Devers came and sat with him on the flight back to San Francisco.

“We sat next to each other on the plane, had a good conversation,” Vitello said. “So, after that conversation … it’s a nonissue.”

Devers, who was traded to the Giants in a blockbuster deal with the Red Sox roughly one year ago, has had a disappointing tenure in San Francisco. After going 1-for-4 with an RBI in the Giants’ 3-1 win over the Athletics, he is hitting .238/.302/.735 with 97 strikeouts in 331 plate appearances.

Posey, who is expected to look to trade some of the team’s highest-paid players at the deadline, has not ruled out shopping Devers. Vitello, however, gave a strong defense of Devers.

“I’m going to go into battle with him anytime,” Vitello said. “If you rewind and listen to my comments [postgame], it was a Father’s Day conversation. As a person, the way he treats my family and especially my dad, I’ll go to battle with him. If he came over to my condo and said, ‘I need your help; you can’t ask about it,’ all I would say is, ‘Whose car we taking?'”

Vitello said he did not take Devers’ defiance personally, saying he did not perceive it as disrespecting him. Devers said it was not his intent to show up his manager.

“It was just heat of the moment,” he said. “Nothing to be read into it. The media in general blows everything out of proportion, and this is a reflection of why I don’t talk to the media.”