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Jon Rahm can be one of the more histrionic players in the game and during his round today he apologised after accidentally hitting a volunteer in the face with a divot.

The Spaniard took a lump out of the grass in frustration after hitting his second shot to the seventh - his 16th - on his way to firing a one-under 69.

"Thanks for reminding me of that. I got a flier on my second shot that went long. It's not a good spot," said the two-time major winner.

"Just out of frustration, I tried to make an air swing, just over the grass, and I wasn't looking, took a divot, and unfortunately I hit a volunteer.

"Yeah, it hit him, and unfortunately it hit him in the shoulder and then the face. Which I couldn't feel any worse [about]. That's why I was there apologising.

"I need to somehow track him down to give him a present because that's inexcusable and for something that could be completely avoidable. Whether it was my intention or not, it was just not good."

Co-leader Martin Kaymer is putting from off the green, fully 54 feet from the hole.

And he's navigated that nicely. Up and down (by rolling it) to save par.

Five holes left of his opening round.

Aaron Rai arrived at Aronimink in good form after contending at last week's Myrtle Beach Classic and he's just picked up back-to-back birdies to move within one of the lead.

The second of those was set up by a stunning shot into the long par-three 17th to just six feet.

Rai is still searching for his first top-10 major finish but he's one heck of a player.

Lots of waiting around on the eighth tee but Matt Fitzpatrick sends a low stinger into the heart of the green.

Justin Rose plays to an almost identical spot while Scottie Scheffler dunks his ball into the right bunker. To give you an idea, this hole is a 245-yard par three. I've got mates that would be laying up.

Scheffler's sand wedge doesn't go that close but he rolls in from 10 feet to save his par. How often does he do that.

The English duo both have to settle for pars after skirting the cup from down town.

Cameron Young is having a bit of an inconsistent round as he heads to the final hole of the front nine at Aronimink Golf Club.

He pays the price for a tee short at the par-three eighth which skids on the green and leaves him needing to chip to back on before two putting for a bogey.

No such trouble for Justin Thomas who goes three under to take a share of the lead after sliding in a putt from six feet.

A strong finish to his front nine has moved Robert MacIntyre into the red.

The left-handed Scot finds the par-five ninth's green with two big blows and tidies up with two putts from there. Two birdies in three holes.

Not to be outdone, Tommy Fleetwood and Chris Gotterup make it a trio of birdies. A needed gain for Fleetwood, too, at the end of a frustrating front nine.

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He's off to a half decent start, Seb.

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Nice one Shane! After a bogey on eight, Lowry responds in tremendous fashion as he chips in from short of the ninth green for an eagle three!

Lowry is renowned for his short game skills and the way he punched that wedge and got it rolling from 39 yards away to send it home was magical.

Justin Thomas holds his nerve to grab par on the seventh,

Thomas' chip from the edge of the green runs 12 feet past the hole to leave him with a tricky putt.

However, the 33-year-old is able to sink it to stay two under.

More straightforward pars for Cameron Young and Keegan Bradley.

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Bob MacIntyre backs up his birdie at the seventh with a not-to-be-sniffed-at par at the 245-yard par-three eighth.

But it's bad news for Tommy Fleetwood, who makes bogey after missing the green. Two bogeys and six pars for the Englishman so far.

Chris Gotterup also fails to make par and joins Fleetwood at two over.

Captain Luke's on the move again.

The European Ryder Cup skipper carded a four-under opening 67 at last year's US PGA at Quail Hollow and he's battling well out there today.

Donald failed to birdie the par-five ninth and dropped a shot at 10, but he's just bounced back at 11 after using the slope at the back of the green to feed his approach back down to a great spot.

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Fairway hit, green hit, birdie putt drained. Scottie Scheffler looks like he means business as he rattles a 40-footer into the back of the cup.

Neither of his two English playing partners can repeat the trick from a little further afield, with Justin Rose's ball grinding to a stop about a foot short and Matt Fitzpatrick, who gets a read off that, nipping a couple of feet past.

Here comes Martin Kaymer!

The 41-year-old is not having a great season on LIV Golf but he's having a great first day here.

He's just drilled in a birdie putt from eight and a half feet at the second (his 11th) to join the flock at three under par.

Shane Lowry hits the bunker on the long par-three eighth, and although he hits a nice splash out of the sand he can't hole the putt and makes a bogey.

Collin Morikawa also makes a four here as he finds the rough just short of the green and then misses his par saver from 10 feet.

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Akshay Bhatia responds to that bogey on the 10th with a birdie on the 11th to get back in among the leading pack.

We told you earlier that Bhatia has got the temperament to go along with his game, and he's showing his fighting spirit again here.

Justin Rose is forced to take a penalty drop after booming his tee shot way right down the right of the sixth hole and being confronted by a tree and an appalling chewed-up patch between the roots.

It costs the Englishman another shot just as world number one Scottie Scheffler starts doing Scheffler things.

A precision approach and putt from eight feet help the American claw that dropped shot from earlier back.

Alex Smalley makes a third birdie in his opening five holes to join the leaders as the latest American to make a decent start to the US PGA Championship.

You may not know too much about Smalley but he's been in decent form on the PGA Tour of late with a T17 at the Cadillac Championship and T17 at the Truist Championship, two big recent Signature Events.

Plenty of players have made good starts today but most have been reeled back in by Aronimink - let's see if Smalley can keep this run going.

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Over at the first, Martin Kaymer's 10th, the two-time major champion is putting for a share of the lead.

It's from 17 and a half feet and it goes close but he'll just knock it in for par.

He stays one shot back.

Bob MacIntyre picks up his first birdie of the championship at the seventh, with an excellent approach from 160 yards leaving him just four feet for a three.

More of that please, Bob!