Dustin Johnson on US PGA Championship at Baltusrol

Dustin Johnson insisted he was unconcerned despite opening the US PGA Championship with a shocking seven-over-par 77 at Baltusrol.

U.S. Open champion Johnson endured a miserable first round at the final major of the year and ended the day in a tie for 143rd position.

Three bogeys in succession took the round away from Johnson, who was already two over after a double at the third, and the 32-year-old pinpointed that disastrous sequence as key to his failure.

"Even after I doubled three, it was fine," he said. "But the three bogeys in a row were just, you know, bad bogeys – all three of them were.

"So that got me not off to the greatest start. It seemed that if I got out of position at all, I got in a really bad spot."

Regardless, Johnson was unperturbed by his round, as he looks to recover sufficiently on Friday in order to make the weekend.

"I felt like I had good practice rounds, [and] this morning I had a good warm-up session," he said. "[I] just struggled. Simple. It's nothing that's off by too much.

"I felt that even throughout the day, I made some good swings. It was just that the ones that were bad ended up in terrible spots. Then the putts, I felt I hit a lot of good putts that just didn't go in.

"Late in the day, the ball was hobbling a little bit."