Rory McIlroy didn't get the best score after the first round but knows he can improve. Photo:

BETHPAGE Four-time major winner Rory McIlroy struggled to a two-over par 72 in Thursday's opening round of the PGA Championship, but a closing birdie brought hope of a weekend turnaround.

The fourth-ranked star from Northern Ireland found himself nine strokes adrift of US leader and defending champion Brooks Koepka after 18 holes at Bethpage Black, but relaxed about his share of 51st along with, among others, Masters winner Tiger Woods.

"I've been out here long enough to know that a first-round score is just a first-round score," McIlroy said. "The golf course is hard enough without looking at other people.

"If I get myself in red numbers for the weekend I'll be pretty happy."

McIlroy missed the fairway and made bogeys on the first and 15 holes, missed a four-footer for par to bogey the par-3 eighth but sank a five-foot putt at 18 for his lone birdie, what he hoped was a sign of better things to come.

"I can't remember the last time I played a round of golf without a birdie. I was like, 'I better birdie this last hole.' Thankfully I did. It was nice to finish that way," McIlroy said.

"Hopefully that birdie on the last was the turning point, finish on a positive note and come back tomorrow and hopefully get into red figures."

McIlroy, whose last major win came at the 2014 PGA, wasn't upset with the birdie chances he had, but unhappy at what he did with them.

"It was either wrong speed at some times or sometimes just a little bit off line either way," McIlroy said.

"Just keep hitting good putts. That's all you can do. It's early in the tournament. Keep hitting good shots. Don't let it frustrate you. Eventually things will turn.

"If you can put the ball in play and give yourself chances, I felt like I gave myself enough chances today to shoot something sort of in the mid-60s. It gives me hope. It gives me hope I can go out tomorrow and shoot a low one."

McIlroy looked forward to an early Friday start after facing well-trod greens Thursday afternoon.

"The greens were starting to get a touch bumpy out there, so that was making it difficult in terms of speed not trying to be too aggressive with your putts and not leaving yourself those three- and four-footers all the time," he said.

"Around this golf course, the margins are fine... Hit enough fairways, felt like I hit enough greens and hit good putts and some days they just find a way to not go in."

AFP