John would work with stone if his career had never taken off.

According to this article:

If acting hadn’t panned out, what would some actors have done? Here are their answers: John C. McGinley, Scrubs “I’ve always worked with stone, so I would apprentice with some artists and then I would be a stone mason. [I’ve built] walks, mantelpieces and walls... in Ireland, I would build walls 20 miles long.”