As for Alex Rodriguez, Canseco says he didn't inject Rodriguez, but that he "introduced Alex to a known supplier of steroids." Canseco didn't mention Rodriguez in the first book because he "hated the bastard." He was worried that people would have "questioned [his] motives" had he included Rodriguez.
Why all the hatred, you ask. Well, Canseco claims that A-Rod was trying to sleep with Canseco's wife. Apparently, even after Canseco had been nice enough to help A-Rod find a friendly steroids supplier, A-Rod kept calling Canseco's wife.
And, in case there's any further confusion about Canseco's true feelings, he ends the chapter by saying:
So A-Rod, if you're reading this book, and if I'm not getting through to you, let's get clear on one thing: I hate your (expletive) guts.
Word. So if A-Rod wouldn’t have chased Canseco’s wife, he would have just been lumped in with all of the other dopes in the book, Juiced. Instead, he was given his own chapter in the latest book. And you have to believe Canseco. Only, it’s hard to swallow that he didn’t want to ruin credibility with the first book. But you can allow him that one brief white lie.