The difference between culpability and common sense can be enormous in sports. You can do nothing wrong yet lose your judgment in a split-second and pay a huge price for your unnecessary bravery. Listen up, Zack Greinke. As your broken collarbone heals, and the Dodgers contemplate the fortune they agreed to pay you to pitch, not to fight giants, the moral will become clear.

Baseball has long had an unwritten rule. In fact, there is even a date associated with it: May 17, 1956. That day 170-pound Ruben Gomez hit 210-pound Joe Adcock with a fastball; then, as Adcock charged the mound, Gomez ran all over the Milwaukee infield and into the safety of his own Giant dugout, leaving the murderous Adcock in futile pursuit. Gomez lived.

Hence, the rule: Think twice before engaging a man who hits home runs for a living and outweighs you by 40 pounds. At such times, morality and causality are not important. Your intent is irrelevant. History is moot. Only physics matters.

Greinke forgot. He not only stood his ground on the mound. In what may be the most foolhardy deed a 195-pound pitcher has ever done: He charged right back at 240-pound Carlos Quentin, the slugger he had just hit in the shoulder with a fastball. Now, Greinke, who ploughed his left shoulder directly into Quentin, will miss weeks and perhaps months, changing the entire landscape of the National League pennant race.

Greinke did nothing wrong. But he sure didn’t do everything right, either. Life is like that. It’s not enough to be, technically, in the right. You have to survive, too. The Dodgers must be delighted that they paid Greinke $146 million so that he could act like a macho idiot.

Sorting out motivation on Greinke-Quentin will never end. True, they have a history. Greinke has hit him twice before. “He always seems to think I’m hitting him on purpose,” Greinke said, “but that’s not the case.” Hmmmm, “always?” Dodger announcer Vin Scully, in real time, said he thought Greinke might have been retaliating for a Dodger who was plunked earlier in the game. Scully once made a mistake, but in another century.

On the other had, Greinke has plausible deniability; few pitchers with a 2-1 lead in the sixth inning would ever dream of drilling the leadoff man with a full-count pitch. Maybe, if the guy had burned down your house that morning, but otherwise, probably not.

Quentin may face discipline. You really aren’t allowed to charge the mound. And he’s a “plate diver” who forces pitchers, out of self-preservation, to pound him inside. That’s why he has been hit more often than anybody in baseball since 2008 and 117 times in all. He invites it. He knows it. That’s why he has no history of mound charging — well, that and a Stanford education. And he didn’t look like he was going to charge Greinke.

That is, until Greinke started talking at him. The only proper words at such times are “oh, bleep” and a look of self-disgust, or, perhaps, “it got away.”During the five slow steps Quentin took toward the mound, deciding what to do, Greinke picked the wrong words. When the pitcher fired down his glove and charged, too, that act may give us a tip as to his state of mind.

There’s a reason that the tape of Nolan Ryan beating up mound-charger Robin Ventura with a dozen rapid headlock uppercuts has been shown a million times: There is no other film like it. Pitchers, who won’t even help their wives lift heavy objects onto high shelves for fear of taxing their arms, have no business going 12 rounds with sluggers who bench-press more than most pitchers weigh.

Only Ryan, a hulk, was big enough to be so stupid brave and pull it off. Old and ornery, The Ryan Express retired the same month. Hell, he didn’t really need that right fist for pitching anymore. Why not thump Ventura with it? Perhaps modern pitchers such as Greinke have seen that film of Ryan too often and need a history lesson.

Long ago, Gomez was notorious for hitting batters, some on orders from manager Leo Durocher. In ’55, a Giant pitch disabled Adcock with a broken left arm, so, when Gomez hit him in the left wrist that day in ’56, the fuse was lit. Here is where the true meaning of “old school” arrives: According to newspaper accounts, Adcock merely chewed out Gomez as he walked to first base. Gomez got another ball from the ump and fired that at Adcock, too, nailing him in the leg. And the chase was on!

Home plate umpire Lee Ballanfant recommended “no further discipline” because “they blew up, that’s all.” No big deal. The second ball? Oh, well.

Perhaps the Dodgers and Padres, when they meet next week, should remember how much provocation was needed before real violence ensued back in ’56. Vin can tell them. For the moment, the two teams seem determined to get more valuable property maimed.

After Thursday’s game in the tunnel under the stands where all teams know they will pass each other, former MVP runner-up Matt Kemp of the Dodgers was yelling at Quentin at point-blank range. All-star Hanley Ramirez, already on the disabled list, got between them. Cy Young winner Clayton Kershaw grabbed Kemp. Padres pitcher Clayton Richard restrained Quentin.

“Later, [female canine],” Kemp reportedly yelled at Quentin.

Come on, fellas, can’t we get some utility men and a backup catcher involved as cannon fodder, not MVPs and guys named Clayton? Of course, NL fans from San Francisco to Cincinnati and Washington to Atlanta may not mind if the outspend-everybody Dodgers were to go all DefCon 1.

What happened between Quentin and Greinke has been going on for more than a century. Neither did much that was out of the ordinary. Many hitters have charged the mound for less. And Greinke may not have done anything amiss whatsoever. What was different was Greinke’s response.

Every pitcher knows the rules of engagement with attacking sluggers. Stay where you are. Let your catcher, first baseman and third baseman sprint toward the mound to aid you. Perhaps, throw your glove at the rhino. Do a boxing shuffle to slow him down. Act like you’re going to throw a punch, but don’t — you may pitch with that hand. Let him throw the first haymakers — and miss, because he always will. This is, after all, a baseball fight.

Then the pitcher bear-hugs the guy, and everybody goes down in a heap of bodies. The “fight” takes half a second. Everyone has stories to tell. And, most important, honor is maintained but (almost) nobody ever gets hurt.

When the Dodgers signed Greinke for that $146 million, they thought they’d examined every inch of his body. They apparently missed two spots: his heart and his brain. One is a size too big, the other a mite too small.

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