The prohibition of the use of PEDs back in Reggie's era was fuzzy. In 1971, the league issued an order that no player could take any prescription medication without a doctor's prescription, and there was no player testing done. Carl Yastrzemski never hit more than 20 homers until he hired some guy named Gene Berdie to be his personal, off-season trainer, then he hit 40 or more in three of the next four years. Then, the league ordered that players not take prescription medications without a prescription, and then he never hit even 30 homers again even though he played for another 13 seasons.
Didn't McGwire's public relations problems begin when he acknowledged that he had been taking a steroids "precursor" that had been prescribed (or over-prescribed) for him by a doctor?
Someone once posited that if a player was using steroids in that era, then you would probably see some of his teammates have boosted power numbers in subsequent years. Yaz's new teammate, Ken Harrelson, went from 12 homers 1967 to 36 homers in 1968, and little Rico Petrocelli went from 12 homers in 1968 to 40 in 1969. Hmm....
Cal Rpikin, Brady Anderson and even Wade Boggs all had single, mysterious poer surge years. So did Davey Johnson and Tommy Harper. Hmm....