Bosch said on CBS News' "60 Minutes" program he injected Rodriguez with human growth hormone and other performance-enhancing drugs prohibited by Major League Baseball.
Rodriguez was banned for the entire 2014 season Saturday in the wake of the Biogenesis scandal after an appeal -- a reduction from his original 211-game suspension for PED use.
"Alex is scared of needles, so at times he would ask me to inject," Bosch told "60 Minutes."
He said he first met with Rodriguez in August 2010, five days after the three-time AL MVP hit his 600th home run, asserting Rodriguez told him he was determined to become the only player in history to hit 800 homers.
Bosch, who was the star witness against Rodriguez in his appeal hearing, claimed he was paid $12,000 per month by the slugger for his services.
The Major League Baseball Players Union denounced MLB's apparent blessing of the segment, saying it amounted to "piling on" after Rodriguez had already been penalized.