After a deflection on the left side, McIlroy tried to break through in the middle repeatedly, but couldn't get past the visitors' defenders.
Not just any spectator - but Gerry McIlroy, father of the four-time major winner.
McIlroy's father survived without major injuries and joked that he would ask for an autograph from the star.
"He just needs to put some ice on his leg, I can sign a bag of frozen peas if he wants," McIlroy laughed after his round, before he a little more worriedly stated that he had made his worst opening round at the US Masters so far in his career.