Accuracy the key for Johnson after 67 at Bellerive

Dustin Johnson enjoyed a "pretty solid" start to his US PGA Championship campaign after ending the day three strokes behind.

Dustin Johnson   -  (Getty Images)

World number one Dustin Johnson believes accuracy is the key to his chances of winning the US PGA Championship after opening with a three-under-par 67.

On the heels of back-to-back top-two finishes, 2016 U.S. Open champion Johnson ended the opening round three strokes adrift of leader Gary Woodland in St Louis on Thursday.

Johnson reached five under at a point, momentarily tying Rickie Fowler for the lead, but he bogeyed two of his last five holes to fall back at Bellerive Country Club.

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"I felt like the day was pretty solid. Hit a lot of putts. Made a few, missed a few. Didn't drive it quite as well as I'd like to. We had a bunch of — hit a few fairways, but I didn't hit as many as I needed to if I wanted to shoot a low score," Johnson said after his round.

Johnson, normally, one of the best drivers of the golf ball on the PGA Tour, hit just 57 per cent of his fairways in round one, and he struggled out of the rough.

"I thought the course played good. It was in good shape. Greens are soft, but it's going to be like that for the rest of the week, I feel like. You know, they still made it fairly difficult. You've got to hit the fairways. You've got to be precise when you're coming in with your irons," said the American star.

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"The fairways are plenty wide. If you miss it, you mis-hit it, it's not going to be on the fairway. You miss the fairway, you're really going to struggle."

Bellerive invited massive crowds on Thursday, with a number of featured groups stalking the fairways in both the morning and afternoon wave.

"We had big crowds out there. They were great. It's a lot of fun to play for a big crowd. I felt like I had a lot of support," Johnson said.