Jimmy Walker
Jimmy Walker leads after the opening day in New JerseyGetty Images

Jimmy Walker leads the US PGA Championship after shooting five-under-par during the first round at the Baltusrol Golf Club in New Jersey. The 37-year-old American is one shot clear of the chasing pack after carding an impressive round of 65.

Walker is closely followed by Argentina's Emiliano Grillo, England's Ross Fisher and Martin Kaymer of Germany, all of whom finished the day on four under-par, while British Open winner Henrik Stenson is a further shot behind.

On a sweltering day in New Jersey, Walker carded six birdies and a solitary bogey on his way to setting the early pace. However, having endured a turbulent season in 2016, Walker refused to get carried away with his early form at the final major of the year.

"I felt like I was ready to go. Winning a major would be huge but there's three days to go," he subsequently said, according to The Independent. "It's just been real stale and stagnant this year. I haven't been making the 15, 18-footers you need to make to start running up the leaderboard and to have high finishes."

The American admitted he is keen to produce an impressive performance at the US PGA to bolster his hopes of appearing at this year's Ryder Cup, too. "I definitely wanted to play Ryder Cup this year and I don't know how much time there is left in that, but I know we do a lot of picks this year (four) and the picks keep going," Walker reflected.

Elsewhere at Baltusrol, former world number one Rory McIlroy sits nine shots off the lead after carding a four-over-par 74. McIlroy missed two birdie putts in his first two holes, and identified his poor form with the putter as the reason for his current troubles.

"I had a couple of chances early on that I could not convert and then missed a couple of greens and did not get up and down and I was always chasing it from there," the 27-year-old star said, according to the BBC.

"I really struggled with the pace. They look much quicker than they are and two or three times I had putts within 12 feet that were downhill and left them short. I need to be more aggressive and shoot something in the mid-60s and get into the weekend."

Defending champion Jason Day shot a respectable 70 on the opening day, but Dustin Johnson recorded a seven-over 77.