He loves playing football. How is it foolish to pursue the thing that makes one happy? To me, the only foolish thing here is judging someone else's career choices. Perhaps I'm being uncharitable here and what you really mean is, "If I were in Murray's situation, I would've chosen baseball because I'd likely have a much longer career, earn more money, and take far less of a beating."

But that's different than calling him foolish. He's not you. He made his decision (presumably) based upon what matters to him, not what matters to you. So how is that foolish?