SAN DIEGO — When Joe Girardi told Alex Rodriguez to grab his glove and get ready to play third base in the bottom of the ninth inning Friday night, the designated hitter said he “felt like a Little Leaguer.”

“I was so excited. I was thrilled,” said Rodriguez, who had not appeared in a game at third base since May 19, 2015. “I wanted the opportunity to go out and play a little third.”

But the Yankees’ four-run rally in the ninth left them a run short in a 7-6 loss to the Padres, so A-Rod didn’t get the chance to use his glove. Girardi made it clear before Saturday night’s game that only a dire situation would cause him to put the 40-year-old A-Rod in the field.

“I don’t think so,” Girardi said. “It’s an emergency thing, and that’s what we were in.”

In Friday night’s 7-6 loss, Girardi already had run through Chase Headley, Rob Refsnyder and Ronald Torreyes. In the case of a tie game, Girardi didn’t want to expend his last bench option, backup catcher Austin Romine. Thus, he told Rodriguez to go into the clubhouse and get his glove for possible use in the bottom of the ninth and perhaps extra innings.

“I sprinted up here,” A-Rod said of the clubhouse run for his glove, “if you want to call it that. My version of that.”

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Rodriguez’s primary concern now is working his way back into the lineup as a full-time DH, which was taken away last week because of a lack of production, particularly against righthanders.

When Girardi and general manager Brian Cashman talked about benching A-Rod against righthanders, it was put in terms of doing something, anything, to spark a moribund offense.

Rodriguez, who had a .223/.260/.385 slash line, eight homers and 28 RBIs in 48 games entering Saturday night, said he’s seen progress, including Friday night, when he pinch hit in the ninth inning and singled off lefthander Matt Thornton.

The single gave him three hits in his last two games and gave him six hits in his last 21 at-bats.

“I’m working really hard with Alan and Marcus,” Rodriguez said of hitting coach Alan Cockrell and assistant hitting coach Marcus Thames. “I think over the last week or so, we’ve gained some good ground. And I think for the last 14 or 15 at-bats, my at-bats have been more professional, I’m swinging at strikes and just making better contact overall.”

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Girardi did not sound quite as enthused. “He’s gotten some hits, yeah,” he said.

Unprompted, the manager then mentioned Carlos Beltran, who has been out with a sore right hamstring.

Girardi has Beltran available as a pinch hitter — he had a pinch-hit double in the ninth inning Friday night — but doesn’t expect the 39-year-old to play the field in San Diego. It seems more than likely that when the Yankees start a three-game series on Monday in Chicago against the White Sox, Beltran will be the DH.

“But the tricky thing is when Carlos comes back,” Girardi continued. “That becomes the tricky thing, how he’s feeling, and always wanting to keep his bat in the lineup. But Alex has gotten some hits.”

Girardi’s desire to see Beltran back in the lineup before A-Rod is well-founded. Beltran has been the club’s most productive hitter this season, leading the Yankees in homers (19), RBIs (53) and slugging percentage (.576).

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For his part, Rodriguez is embracing the doubt, the ever-increasing narrative that he, as a soon-to-be 41-year-old come July 27, is done.

“I love the challenge,” he said. “It’s not the first time people have said he can’t do this or can’t do that. I’m going to continue to work my [butt] off day-in and day-out. I’m excited about the challenge and I think I’m going to do lot of damage. Look, there’s no question our team is best when I’m in the middle of the lineup producing.”