McIlroy and Rose were among the early starters at Oakdale Country Club where play began two days after the announcement of a partnership between the PGA Tour and Saudi Arabia's Public Investment Fund, which controls LIV Golf, shook the golf world.

"Rosie and I said, 'all right, no chatting until lunch' so that we can actually concentrate on what we're doing out there," said two-time defending champion McIlroy.

"We started to get in a conversation walking down the first and we're like, 'No, let's stop this. Let's just focus on our golf and we'll say what we want to say when we get inside.'"

Critics of LIV Golf consider the lucrative circuit, which features no cuts and 54-hole events instead of the traditional 72, nothing more than an attempt to "sportswash" Saudi Arabia's record of human rights violations.

McIlroy has been the PGA Tour's most outspoken golfer against LIV Golf and the last two days, which included his much-anticipated press conference on Wednesday, took a toll.

"I got a good night's sleep last night. So it was nice to sort of recharge the batteries," said McIlroy, who added that the news conference was the most uncomfortable he's felt in the last 12 months.

"I would say my energy levels on Tuesday and Wednesday were diminishing quite quickly."

McIlroy shot a one-under-par 71 in his opening round, which was played amid the smell of smoke lingering in the air due to the many uncontrolled forest fires burning across Canada.

World number three McIlroy, bidding to become the first player to record three consecutive wins at a tournament since Steve Stricker in the John Deere Classic from 2009-11, capped his round in style with an eight-foot birdie.

While it may not have been his best performance, McIlroy was just happy to be back on the course.

"So it was nice to play a round of golf and focus on something else for those five hours we were out there," said McIlroy.