Two-time champion Ernie Els said he was badly affected by his opening drive at the Open at Royal Liverpool, which hit a spectator in the face.
The South African three-putted from 18 inches for a triple-bogey seven and went out in 42, seven over par.
Els, 44, improved on the back nine but finished with a disappointing 79.
"I felt pretty bad about it. I hit the guy, who was probably in his 60s, right in the face and there was blood everywhere," said Els.
"I probably should have told the starter to move the people back on the left side, but I didn't do that.
"You think the worst. It was like a bullet coming at him so he must have been in total shock. Hopefully he's better now, but it wasn't very nice."
On the effect it had on his round, which left him 13 shots behind leader Rory McIlroy, Els added: "I was thinking about him. I was quite rattled.
"I was kind of finished and then started missing short putts. It was a nightmare so I'd like to put it behind me.
"I just hope the gentleman feels better because he looked really bad when I left him there."
Els's round took another bizarre twist when his drive at the last was disrupted by a toad, which the four-time major champion had to usher from the tee box.
Els's playing partners, defending champion Phil Mickelson and Masters champion Bubba Watson, fared only slightly better with rounds of 74 and 76 respectively.
Watson complained about the number of people following the group inside the ropes but admitted he had only himself to blame for a poor round.
Having played the first 10 holes in one under, Watson was heard complaining about the amount of people on the 11th, where he carded a triple-bogey seven.
"I lost focus on 11 - it was a short hole, middle of the fairway, I just forgot what I was doing," said the American.
"There was about 40 people in our fairway, inside the ropes with cameramen, and a bunch of other people.
"It makes it tough for me because I lose focus real fast. But nobody else was having that problem, it was just me, it was my fault."
Asked whether he thought there were too many people inside the ropes, Mickelson said: "It's not a problem, it's just a different culture than what we're used to, that's all."