Rory McIlroy said he would expect a “couple of mistakes” in his game after a three-week lay-off as he kept himself in early contention to defend his title at the Wells Fargo Championship.

The Northern Irishman birdied five of his first six holes of his opening round for a three-under-par 67.

Jason Day leads on seven under, while England’s Aaron Rai and Callum Tarren are both in contention at five under.

“It could have been 65 or a 64,” said McIlroy. “It’s still a good start.”

McIlroy made a double-bogey on his 13th hole of the day at TPC Potomac in Maryland, in the USA, but found two late birdies and added: “That was a nice bounce back to birdie both of those holes. I said to myself walking off the green, if I could just get back to three under by the end of the day after that, I would be pretty happy.

“I think that in the first week back after three weeks off, there are maybe going to be a couple of mistakes in there.”

McIlroy – who has won the event three times – is tied for 17th.

Australia’s Day won the tournament in 2018 in what was the last of his 12 wins on the PGA Tour.

The 34-year-old has slipped from being world number one in 2016 to a rank of 127 at the start of this week’s event.

He dropped one shot all day and hit eight birdies, leaving him a shot clear of American Joel Dahmen.