Over brunch with my husband and one of my best guy friends last weekend, conversation turned, as it does, to Major League Baseball, doping and the nature of sin.

“A-Rod, possibly the greatest baseball player in the history of the game, will never, ever be in the Hall of Fame,” my friend said with a mixture of anger and sadness. “All those guys — Bonds, Roger Clemens — none of them will be in the Hall of Fame.”

“And they shouldn’t be,” my husband added.

New York Yankees slugger Alex Rodriguez is the latest MLB player accused of using performance-enhancing drugs.

Barry Bonds was among major leaguers listed as customers of the Bay Area Laboratory Co-Operative (BALCO), purveyors of illegal steroids. He’s denied the charges, but was indicted for perjury and obstruction of justice in the BALCO investigation. His obstruction of justice trial is set to begin next month.

Clemens, certainly one of the greatest pitchers of all time, famously was accused of doping in Jose Canseco’s book Juiced: Wild Times, Rampant ‘Roids, Smash Hits & How Baseball Got Big, an accusation Clemens has vigorously denied.

Between sips of coffee, as his ire mounted, my friend proclaimed: “They tarnished the sanctity of our beloved national pastime!”

And that is, at least to diehard baseball fans, an unforgivable sin.

While I enjoy a good baseball game and consider myself a Cubs fan, I can’t recite statistics or recall memorable plays, and usually I have to ask someone else the relief pitcher’s name. But I understand the sense of betrayal my husband and friend feel.

There was an unspoken, sacred trust between the players and fans that was broken. Irreparably.

Even after his emotional, confession-filled news conference Tuesday, I doubt whether A-Rod will be the same kind of hero he once was. After admitting he had used a substance he called “Boli” that apparently could be purchased in the Dominican Republic between 2001 and 2003 when he was “naïve” and “young,” A-Rod pleaded: “The only thing I can ask of the American people is to judge me from this day forward.”

That’s a tall order when it comes to unforgivable sins.

We Americans love a comeback story — be it Whitney Houston battling back demons of addiction to retake the stage with her unmatched voice in all its glory, Paul Rubens once again making people laugh without wincing, or welcoming Martha Stewart and her “good things” back into our homes after her stint in white-collar prison.

We cherish rags-to-riches stories, and tales of people emerging phoenix-like from the ashes of their own self-destruction.

But there are certain things we don’t forgive.

Harming a child in any way — especially if you’re a coach, a teacher, or a member of the clergy.

Abusing and/or murdering your wife (particularly if you’re acquitted and show no remorse when everyone thinks you’re guilty as hell).

Blatant racism, at least when it’s caught on tape (video or audio).

Hypocrisy, most notably the variety where you lobby very publicly against gay marriage and then get caught having sex with a male prostitute.

“It’s hypocrisy more than anything in our society that we consider unforgivable,” said John Portmann, a professor of religious studies at the University of Virginia and author of A History of Sin: Its Evolution to Today and Beyond.

Theologically speaking, though, what qualifies as an unforgivable sin?

In the Bible, both the Hebrew Scriptures and the New Testament mention something known as the “eternal” or “unpardonable” sin. Once you commit such a sin, according to some interpretations, salvation is impossible.

In the Jewish tradition, while the Torah (in Exodus) says humankind’s ability to sin never surpasses God’s capacity to forgive, there are three sins you’re NEVER supposed to commit: idolatry, murder, and adultery (which included not only cheating on your spouse, but also homosexual acts and having sex with your wife while she was menstruating.)

According to the gospel of St. Matthew, Jesus himself described an unpardonable sin as “blaspheming” or “grieving” the Holy Spirit. What that is, exactly, Jesus doesn’t say. I guess if you do commit the Big One, you’ll know it. Game over.

Portmann believes the pariah status sports figures who are caught cheating in one way or another acquire is connected to a perception “that they have done some sort of invisible damage to children coming up who looked up to them.”

When those who have been accused of cheating (or doping or perjury about doping, etc.) publicly confess and ask for forgiveness, they often find the forgiveness they seek.

Take the fallen Olympian Marion Jones, who served a six-month prison term last year for perjuring herself during the BALCO investigation. I bet Jones will be allowed to make a comeback some day because she showed contrition. She confessed humbly and publicly.

“With a great amount of shame … I stand before you and tell you that I have betrayed your trust,” she said tearfully on the courthouse steps the day she pleaded guilty. “You have the right to be angry with me … I have let my country down and I have let myself down.”

That was a convincing apology.

“What could really help A-Rod is if he would go public. Cry. Say he’s very, very sorry; admit that he’s lied and he’s broken the rules,” Portmann said Tuesday morning, just a few minutes before the Yankees great appeared at a news conference and did just that.

A-Rod’s quivering lip Tuesday as he confessed that, among other things, he “knew we weren’t taking Tic Tacs,” may have saved more than just his career.

It might keep him off the road to pop-culture perdition, too.

Cathleen Falsani is the religion columnist for the Chicago Sun-Times and author of the new book Sin Boldly: A Field Guide for Grace.