It came through clear one day when I was listening to the song on the radio. And I was relieved to hear that I had heard it wrong, because had it really been about Hank Aaron it would have been inaccurate.
1) There is no way Bruce Springsteen and Hank Aaron went to the same high school at the same time.
2) "Hammerin' Hank" was an outfielder and one of the best power hitters of all time. I guess he COULD have been a good pitcher in high school, but I'm sure his accomplishments at the plate were more prominent and worth singing about than his "speed ball".