NEW YORK - He’s a sure Hall of Famer, perhaps the next home-run king. Yet, come October, Alex Rodriguez must prove he belongs.

Prove that he belongs on the Yankees. Prove he belongs among the greats. Prove that when it’s time to come up big, he doesn’t disappear.

It’s as simple as 1-2-3.

A total of 123 players have had RBIs during the past two postseasons. Rodriguez isn’t one of them. So when the red-white-and-blue bunting is draped over the railings and the teams line up along the foul lines for the postseason opener, his 50-plus homers and 150 or so RBIs during a sizzling season will be like last year’s report card, collecting dust on a shelf.

Yankees fans will be thinking about different numbers: 1-for-14 against Detroit in last year’s division series and 2-for-15 versus the Angels the previous year. Including the end of New York’s 2004 AL championship series collapse against Boston, A-Rod is 4-for-41 (.098) with no RBIs in his last 12 postseason games.

And here’s the most shocking stat: He’s hitless in his last 15 postseason at-bats with runners in scoring position, striking out six times.

For Joe Torre, the math is far simpler in fans’ minds: No World Series titles.

“I think that’s going to follow him,” the Yankees manager said, comparing A-Rod’s situation to that of John Elway.

“I don’t think there was any doubt about John Elway’s ability and the fact that he was going to go to the Hall of Fame and the fact that he was pretty damn special,” Torre said, “but all of a sudden, he didn’t gain that credibility until he won.”

Pinstriped hero or Bronx reject? A-Rod’s place in history could be defined in the next few weeks.

Always the center of attention because of his bat and record contract, Rodriguez could be in his final weeks with the Yankees — he can opt out of the final three seasons of his $252 million, 10-year contract during the 10 days after the World Series and become a free agent.

His regular season this year is unmatched — at 32, he became the youngest player to reach 500 homers and he’ll likely win his third AL MVP award.

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In Torre’s eyes, A-Rod’s big regular seasons won’t be forgotten in years to come and will gain appreciation with perspective. At times, especially when Rodriguez hit 14 home runs during April, A-Rod kept the Yankees from sinking even farther behind in the postseason chase before the team started to click.

But in the clubhouse, where Derek Jeter, Mariano Rivera, Andy Pettitte and Jorge Posada are icons because of their World Series rings, players know the ultimate title is the only one that really counts. The Yankees have been stuck on 26 World Series championships since 2000, when they won for the fourth time in five years, and All-Stars have come in and out the clubhouse door with the speed of commuters going through subway turnstiles.

“We have to produce or it’s a down year for us,” Johnny Damon said.

A-Rod, circumspect in his comments this season, doesn’t think about whether others will judge him solely on the postseason.

“I can’t speak for the fans,” he said before a game against Baltimore this week. “The most important thing you do is each and every day in front of you.”

Two years ago, coming off a regular season that would earn him his second MVP, he put just 10 balls in play during five games against the Angels. They pitched off the plate — he saw 47 balls and 46 strikes, according to STATS Inc. — and Rodriguez became overanxious.

“I played great baseball all year, and I played like a dog the last five days,” is how he summed it up then.