Rory McIlroy insists the disappointment of his nightmare start to The Open was not enhanced by it occurring at Royal Portrush.

It was an opening round to forget for McIlroy, who started with a quadruple-bogey eight and finished with a seven on the par-four 18th en route to an eight-over-par 79.

That was 12 behind early clubhouse leader Shane Lowry, while world number one Brooks Koepka was also at four under through 14 holes.

McIlroy's round did not follow the script for the local hero and he faces a monumental battle to even make the weekend for Portrush's first Open Championship since 1951.

"I'd be disappointed regardless, whether it was here or St Andrews or Birkdale or any of the other tournaments or majors," he said. "I'm disappointed, but at the end of the day I'm still the same person.

"I'm going to go back and see my family, see my friends, and hopefully they don't think any less of me after a performance like that. I'll dust myself off and come back out tomorrow and try to do better.

"I didn't give a very good account of myself out there and I can definitely play better, as all of you know. It's about doing the simple stuff - getting the ball in the fairway, missing it in the right spots if you do miss it. 

"The things I usually do pretty well I didn't do today and it made for a tough start."

McIlroy said his opening hole did not play on his mind and actually focused his game as he felt the situation could not get worse.

"It almost settled me down. It was almost like, well, that's sort of the worst that can happen. Put your head down and keep going," he added. "I'm not saying that it was the ideal start. But at that point what else can go wrong? 

"I just put my head down and tried to keep hitting good shots and I did that for the next 13 or 14 holes. I just let it go a little bit at the end."