Rory McIlroy fires a 66 to grab a share of the first round lead in the Hero World Challenge

The Northern Irishman's understanding of the capricious nature of his sport was prompted by a chaotic double bogey-7 at the ninth hole being immediately followed by a brilliant homeward nine of 5-under 31.

"It was nice to play the back nine the way I did and put myself back in the tournament," he added.

Another four men - Tony Finau, Patrick Reed, Viktor Hovland and Collin Morikawa - carded 68s for tied seventh and, in all, 18 of the 20 man field ended the first day in red numbers.

McIlroy was pleased with his effort, but all too aware that he missed key opportunities to go lower.

"I played the par-5s in even par and there are five par 5s here," he said. "I should be taking care of those.

"That's something I'm going to need to do over the next three days because I can't rely on doing what I did today. I made three 2s out there, one on a par-4. I need to take care of the par-5s just to make it a little more stress-free."

What pleased him was that his lap backed up his belief that something important has changed in these late months of the year.

"I really turned a corner after the Ryder Cup," he insisted. "I've been sort of saying that all along. I feel like I found something those few weeks between the Ryder Cup and the CJ Cup.

"Winning the CJ was a bonus, it sort of came out of nowhere and gave me some confidence. I had the lead going into the last day in Dubai and off to another good start here.

"So the three starts since the Ryder Cup have been really good. I've shot some good scores, low scores. The game's feeling a lot better and it's another chance to get into contention.

"The more I get into that position and have those experiences, the more comfortable I'm going to be going forward."

With the tournament wide open, let's take a look at what the rest of the first round pace-setters had to say.

"I feel like I've been able to improve my game every single year, but also mentally; feeling more comfortable and feeling like I can compete in big-time events and majors. I just feel like I belong and that's a big part of playing good in big-time events. Obviously, you can stripe it all day, but if you don't have the mentality that you can win out there, it's going to be pretty tough for you to put some good numbers out there. So my game itself has improved and I feel like mentally I'm in a better spot as well.

"I've said before, when I first got on Tour, mentally I had no chance. I felt like I was always pretty mentally strong and ready, but there were events at the beginning of my career where I was like, I have no idea if I have what it takes to be out here."

"I took a month completely off, didn't touch a golf club and slowly started ramping it up. The last two or three weeks I've been playing more golf here and there, and the last 10 days I played every day, been playing really nicely. It's just tough when you haven't played competitively to get back in the rhythm of things.

"It's probably the longest break I've had in my professional career. It was a little scary taking over a month off because I haven't done that in a while, wondering if you're going to come back and still have it. But mentally and physically I needed the break. I just wasn't ready to play."

"I worked my tail off over the last two months and I see the light at the end of the tunnel. I'm damn close and it was nice to see shots come out the right window, right flight, right shape, right spin, right everything. Just go work on it and get better and better every day.

"It feels like the last two years have been a struggle except for the majors and WGCs. I think only four top-20s in the last two years are outside of WGCs. It's not been very good."

"I've been wanting to do it for a while and it finally worked out with the schedule to get it done. That's why I keep walking around with the sunglasses. I don't wear those too often, just trying to protect the eyes. Yeah, it was nice to get that done and try to put it to the test here this week."