SAN DIEGO — Zack Greinke’s pitch sailed up and into Carlos Quentin’s upper left arm, and it was on.

A little personal history was at play, as were rules that aren’t in any rule book.

Now the Dodgers will be without their $147 million pitcher for at least eight weeks and Quentin was suspended for eight games by Major League Baseball, pending an appeal, because of baseball culture and its fuzzy, unspoken guidelines on just when and how it’s OK to bean someone.

After Quentin got hit, the San Diego Padres’ slugger took a few steps onto the grass. When Greinke, Los Angeles’ prize offseason signing, appeared to say something, Quentin tossed his bat aside and rushed the mound.

The 6-foot-2, 195-pound Greinke dropped his glove and the two players lowered their shoulders. The 6-2, 240-pound Quentin — who starred as an outside linebacker in high school — slammed into the pitcher.

Quentin and Greinke ended up at the bottom of a huge scrum as players from both sides ran onto the field and jumped in Thursday night.

Greinke took the brunt of the blow, breaking his left collarbone.