Griffey: What might have been
This is something I put in my Reds Insider for the paper (and you get it with it spending the $1.50):
Ken Griffey hit a home run in roughly every 4.2 games as a Red going into this season. He missed a total of 435 games as a Red.
So if he hit home runs at that rate and played in every game as a Red, he would have hit 103 more home runs. Add that to the 563 he had going into the season, and it would have put him at 666 entering 2007.
Of course, Griffey would not have played every game. But even if he missed an average of 10 a year, he'd be in reach of 700. And Barry Bonds would only be looking at holding the record temporarily.