Mariano Rivera and his family celebrate Mo's election to the Baseball Hall of Fame, then go crazy when hearing he is the first unanimous selection. (0:33)

In Mariano Rivera's playing days, he believed, as a general rule, that you shouldn't fraternize with opposing hitters. At All-Star Games, he was polite to his temporary teammates, especially the pitchers, but he wasn't really into hanging out with the sluggers.

Rivera -- who became on Tuesday the first player ever elected unanimously to the Hall of Fame by the BBWAA -- believed you should keep your emotions locked down in success or failure. When you won, you should act like it was the expected result, and if you lost, you should never, ever allow an opponent to think they had accomplished more than just winning that day's game.

As the Diamondbacks swarmed the field to celebrate Luis Gonzalez's series-winning bloop single in Game 7 of the 2001 World Series, Rivera walked off the field at the same pace as in those hundreds of instances he clinched a save and moved to the catcher to exchange a handshake. His expression never really changed as he stepped into the visitors dugout, or when he responded to dozens of questions in the clubhouse afterward. This was the gracious face of Rivera that fans and opponents came to know and respect.

And it was a façade.

A mask. To cover for the monstrous, uncharitable competitor that resided within the right-hander. When Rivera is inducted into the Baseball Hall of Fame this summer, the greatest hitters in the world will surround him on the dais, and if you gave the right-hander truth serum, he almost certainly would tell you he could've dominated any of them on their best day.

I learned this about Rivera in the four seasons I covered the Yankees as a beat writer for The New York Times. Rivera was uniformly genial in the clubhouse, easy with a laugh and mostly measured in his words. But there were moments in which the ambitious, cutthroat antagonist escaped.

Rivera pitched 141 innings in the postseason, about the equivalent of two regular seasons of work for a fully deployed reliever, and in all of that time, he allowed two homers. Jay Payton of the Mets hit the second of those, in the 2000 World Series, in the midst of a rally that fell short in Game 2. Rivera made 63 playoff and World Series appearances after that and didn't allow another.

The first homer Rivera allowed in his 86 postseason games was hit by Sandy Alomar Jr. of the Indians, in a pivotal playoff moment in 1997. This was at the end of Rivera's first season as the Yankees' closer, in Game 4 of the American League Division Series. In a best-of-five series against the Indians, the Yankees led two games to one, and in the eighth inning of Game 4, they were ahead 2-1. When manager Joe Torre summoned Rivera to pitch, the Yankees were five outs away from advancing.

In Rivera's first seasons as a reliever, he threw in the mid-90s, his fastball sometimes registering above that, in those days when some radar guns emitted numbers higher than others. With two outs, the Indians catcher stepped in to bat. Rivera whipped a fastball over the outside part of the strike zone, at 94 mph, and Alomar, a right-handed hitter, drove it to right field, a high fly ball. Paul O'Neill retreated to the wall, feeling for the fence, thinking he might have a shot for a leaping catch.

But the ball carried over O'Neill's glove, into the extended hands of the fans sitting in the first row of seats. (You can see the home run here.) O'Neill slammed his glove onto the warning track, in a moment that might make Red Sox pitcher Eduardo Rodriguez feel a little better about what he did in Game 4 of last year's World Series. Alomar raised both arms over his head, circling the bases with the game-tying run.

"That Alomar home run really doesn't bother you, does it?



'No,' he said, the tone of his voice changing, sort of like when Linda Blair's character becomes possessed in The Exorcist. The stately curtain of comportment had just dropped, and the untethered Rivera launched emotional projectiles from deep within his competitive heart.



'You know why? Because I made that home run.'



At first, I wasn't sure what he meant; I wasn't sure if he was kidding.



He wasn't."

Cleveland scored again in the ninth inning to win that game, and the Indians prevailed again in Game 5 to eliminate the Yankees, and one of the primary storylines that hovered over Torre's team in the spring training that followed was whether Rivera would recover emotionally from that failure. Many closers had seemingly lost their confidence after a postseason moment like Rivera experienced, from the tragic example of Donnie Moore to others like Calvin Schiraldi and Mark Wohlers.

When Rivera first appeared at Yankees camp, he was asked about the Alomar homer, and when national writers circulated through New York's camp in Tampa in the days to come, he was asked about it some more. In 1998, the Yankees won 64 of their first 84 games, on their way to 114 regular-season victories. But all summer long, Rivera continued to hear the same questions and give the same polite answers. The Yankees clinched a playoff spot before September, leaving a month of columnist assessment about a possible Achilles' heel in this juggernaut -- and of course, the greatest unknown was whether the second-year closer might have a crisis of confidence once the team played meaningful games in October again.

I must've heard Rivera patiently respond to those questions a dozen or so times, and after mulling over the consistency of his answers, I stopped by his locker one day very late in the season.

That Alomar home run really doesn't bother you, does it?

"No," he said, the tone of his voice changing, sort of like Linda Blair's did in "The Exorcist." The stately curtain of comportment had just dropped, and the untethered Rivera launched emotional projectiles from deep within his competitive heart.

"You know why? Because I made that home run."

At first, I wasn't sure what he meant; I wasn't sure if he was kidding.

He wasn't.

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I made Alomar's home run, he reiterated.

Rivera explained. He had thrown his fastball -- one of the best in baseball at that time, when a mid-90s fastball wasn't common -- over the outside corner. Alomar, the unvarnished Rivera said, stuck out his bat. Alomar had hit the ball squarely, he allowed, but it wasn't like he'd taken a big hack, and the ball had barely carried over O'Neill's glove and the right-field wall.

The power of that home run, Rivera concluded, was generated by Rivera. Not Alomar. As far as Rivera was concerned, he created Alomar's home run. Rivera, and not Alomar, had controlled the moment.

I walked away awed by his instinctive mental gymnastics that so easily somersaulted him to a place of emotional comfort.

Alomar's home run, as it turned out, was the lone pivotal postseason home run Rivera surrendered in his entire career. Five hundred twenty-seven batters faced in the playoffs and the World Series, and just 11 earned runs. A 0.70 ERA.

Those numbers are impossible, constructed on more than his ability to spin a cut fastball with unusual movement. Hopefully, the Hall of Fame can find room for the phrase "Mental Ninja" on the plaque of arguably the greatest postseason performer in baseball history.