Defensive formation on 3rd and 16 in Eagles game.

Should you always play zone on 3rd and 15? It looked to me like it was man coverage with a Safety over the top. What is wrong with that call?
Always? Maybe you can find a circumstance that you wouldn't. But with the clock where it was, the amount of time our defense had been on the field during the game and the desire to keep the ball in front of the sticks, zone was the right call today. Why leave it to a tired single high safety. I don't know what the argument for man coverage would be in those circumstances.