It's not like a normal player cannot pull off these one-off shots and as said by the others in this thread, it does happen. Our problem is that we hit one, get high off it, and continue to try and hit the amazing shots that Fed makes seem easy.
That's the thing with players of his caliber. They make things seem really easy. The same shots you have to be high on endorphins and in the zone to hit, he hits like it's another simple shot. But hey, look at it this way... at one point in time, he couldn't hit them either.