The 25-year-old former U.S. amateur standout had his way with the pristine 7,079-yard piece of real estate and before the Mackenzie Express had ground to a halt, he was in the clubhouse with an 11-under 61.
European Tour star Jean Van de Velde, Brad Fritsch of Manotick, Ont. and American Brian Guetz came in with 64 to at least keep Mackenzie on the radar.
Scott Hawley of Ottawa and Americans Will Yanagisawa, Brendan Steele and Justin Snelling each opened with 65 and are four shots back.
Nine others fired 66, including Canadians Wes Heffernan, Dale Vallely, Adam Speirs and Glenn Collins.
Matt McQuillan of Kingston, Ont., the 2005 TELUS Edmonton Open champion, used an 8-iron to ace the 164-yard, par-3 sixth en route to a 67.
The final group finished play at 8:35 pm EDT, just as dusk turned to night at Quatre Domaines.
Heavy rain overnight left parts of the course unplayable, delaying the morning wave of tee times by an hour. Once the balls were in the air, however, it was target practice as players took advantage of cushioned greens and, with no wind, perfect scoring conditions.
It didnt take long for Mackenzie to comply.
After a somewhat routine 4-under 32 on his front side, the ex-First Team NCAA All-American (University of Washington) tore it up to the tune of a 7-under 29 on the inbound nine, highlighted by a 25-foot eagle on number one, his tenth hole of the day.
I dont think anyone wakes up and thinks about shooting 61, said Mackenzie, who had the eagle and five birdies after making the turn. I just tried to get something going. I did everything you need to do to put up a low number. I just kept the pedal to the metal and didnt let up.
Its a great championship golf course; its too bad the weather didnt cooperate. They did a wonderful job getting it ready for us (early Thursday).
Of the 156 players in the starting field, 105 managed to break par Thursday.
Mackenzie could have been one shot off the magical 59 had he not lipped out a short putt on his closing hole of the day.
While the number bettered the old course benchmark by two shots, the 61 will not go in the official record books. The waterlogged course forced tournament officials to put the lift, clean and place rule in effect Thursday morning, meaning any course record set is deemed unofficial.
Aussie Scott Hend posted the 63 in 2001, a mark that was equalled later in the week by recent Nationwide Tour champion Doug LaBelle and the late Jace Bugg, who passed away from leukemia in 2003.
It doesnt really matter to me, added Mackenzie when told of the technicality. No matter what, a 61 is a 61.
Van de Velde, weary from travelling across the Atlantic and adjusting to the Canadian time zone, ended his day in grand style. Standing 267 yards from the pin on the par-5 18th, he crushed a 3-wood second shot to ten feet before jarring the eagle putt.
Im tired'its bedtime where I come from, he said with a laugh. It was just a great round of golf altogether.
64 is a fantastic score anytime'when you start your week like that, its even better.
Fritsch turned at minus-2 before birdies on 10, 11 and 12 ignited a 30 on his back nine. Knowing Mackenzie was in the house at 11-under, Fritsch, who played in the U.S. Open last month, felt he had to take a few chances to try to reel in the Washington native.
I saw a leaderboard for the first time on seven and thought Holy cow, Ive got some work to do, reasoned Fritsch. It was more of a wake up call that the course was playing pretty easy more than anything. It was just one of those days.
Five months after his first Canadian Tour title in Austin, Tex., Guetz has put himself in early position to improve on his fourth-place perch on the Rolex money list. While he was impressed with his own round, Guetz was quick to tip his cap to Mackenzie.
I dont care where you are playing, what the conditions are, anything, thats just a great score, said Guetz of Mackenzies day. I just went out there and did what I could. Its not a quick race, its a marathon, and I am still right there.
Mackenzie also helped lead the U.S. team to the Walker Cup in 2003.
There is probably no way I am going to shoot that number again, he admitted. Its going to be tough to back that up, but Ill just come out tomorrow and see where it goes.
Minutes before Mackenzie came in, Hawley put the finishing touches on his own bogey-free round of 65.
For a brief time, the number gave Hawley the clubhouse lead. Once dusk had settled over Quatre Domaines, Hawley must have thought he was standing still.
None of my drives got me into any trouble, so I had 18 chances at birdie, he said shortly after signing his scorecard. Ball in hand, soft greens, theres not much the course can do to fight back. But if you can put up those kinds of numbers, youll be right in the mix. With these conditions, if you shoot 5-under, youll get passed.
Or, for that matter, 7-under, as Mackenzie proved half an hour later.