Jon Rahm struggled to an opening-round 76 at the PGA Championship

World No 1 Jon Rahm remains hopeful of fighting his way back into the PGA Championship despite making a nightmare start to his bid for back-to-back major titles at Oak Hill.

The Masters champion, already a four-time winner on the PGA Tour this year, struggled in all areas of his game as he stuttered to a six-over 76 during a frost-delayed opening round.

Rahm was under par after six holes of his round before carding five bogeys in a six-hole stretch, with the pre-tournament favourite dropping further shots along the closing stretch to equal the second-highest opening round of his PGA Tour career.

• Rory McIlroy 'fighting something' during messy start
• PGA Championship: Latest updates and highlights
• Get Sky Sports | Stream the biggest moments on NOW

Rahm is chasing a fifth victory of the year and a third major title of his career

"The six holes of the day I played really good," Rahm said. "Put myself in a good spot and after that I found myself battling. Couldn't find the fairway and the fairways that I missed cost me bogeys.

"The main thing on this course is hitting the fairway. If you put the ball in the fairway you can actually give yourself a lot of good chances. Even 18 [on Thursday] was playing downwind, so if you put it on the fairway, you can have a good look at maybe hitting it close and that's what I didn't do.

"The only thing I can look back on myself is the three short putts I missed on the back nine. If I make those putts then I shoot three over, which is not the worst-case scenario."

Rahm started his week with a 15-foot birdie at the 10th, leaving him three strokes better than after the opening hole of his victory at The Masters, with the Spaniard missing an eight-foot opportunity at the driveable 14th before starting his slide with a bogey run around the turn.

The world No 1 missed from 12 feet to save par the 16th and bogeyed his next two holes after errant drives, with Rahm following a dropped shot at the second by missing from five feet at the next.

He failed to get up and down from the greenside bunker to save par at the sixth and carded a three-putt double-bogey at the seventh, with the two-time major winner 10 strokes behind clubhouse leader Bryson DeChambeau despite birdieing his penultimate hole.

"It wasn't my best swings on the last two holes and made a birdie and a par, so there's many ways to do this," Rahm added. "You don't need to play perfect. If I can somehow manage a low one [on Friday] and find myself close to even par going into Sunday, I think I'll have a decent chance."

Please use Chrome browser for a more accessible video player

Ryan Fox speaks about recently overcoming pneumonia and the sleepless nights he's experiencing after welcoming his second child in the build-up to the 2023 PGA Championship

Scheffler enjoys bogey-free start

Scottie Scheffler, the only player who can leapfrog Jon Rahm at the top of the world rankings this week, was a shot behind DeChambeau after carding a brilliant bogey-free 67.

Scheffler opened with four straight pars and followed 15-foot birdies at the 14th and the fifth by adding another from close range at the par-four eighth, seeing him card the first bogey-free round of his major career.

Scottie Scheffler is already a winner this season at the WM Phoenix Open and The Players

"[On Thursday] was probably the easiest conditions we'll see all week with the golf course," Scheffler said. "So getting around with no bogeys was really good. I mean, that's pretty much how I shot three under. There's not really many birdie opportunities out there. So if you can limit the mistakes, good things will happen.

"This place is pretty tough. I came into [the first] round just trying to play solid golf. I kept the course in front of me for the most part and hit some really good tee shots on the important holes. Then I had some nice saves as well."

Watch the 105th PGA Championship throughout the week live on Sky Sports. Live coverage continues on Friday from 1pm on Sky Sports Golf.