The top of the leaderboard may be dominated by Americans - with Tommy Fleetwood the English representative - but there are three Italians in the mix too.

The Molinari brothers - Edoardo and Francesco - as well as US Open debutant Guido Migliozzi are all on one under, three back from leader Rodgers.

That bogey for Koepka means Patrick Rodgers is on his own on four under.

The 28-year-old American had made it back-to-back birdies with another one on the 13th shortly before Koepka's blunder.

Rodgers' previous best finish was tied for 41st in 2018, but he started brightly this year with birdies on the first and fifth. Long way to go of course...

Phil Mickelson hits his seventh green in regulation with a straightforward knock into the centre of the second.

Xander Schauffele, from 125 yards, with wedge in hand, is right on line, but about 10 yards short and the spin takes the ball further away.

Recovery central.

Brooks Koepka is forced to take a drop after that errant tee shot but he chips a fantastic recovery effort on to the green then sinks a real gut-check putt.

A bogey that's as good as a birdie in many ways.

Collin Morikawa and Justin Thomas also register bogeys on what was a pretty nightmare hole for all three Americans.

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Phil Mickelson and Xander Schauffele hit two solid putts each and walk off the first green with pars.

On to the second tee. Mickelson is out with his 2-wood again and drills a low one down the middle. Schauffele is a touch right but he should be OK.

Brooks Koepka may have gone a bit wayward on the last hole but in general he is laying down a stronger marker for his supposed arch-enemy Bryson DeChambeau.

The social media feud between the two seems to have reached its peak in recent weeks, but what do you make of it? Is it good or bad for the game? Do the more cynical among you suspect it might have something to do with the new PGA Tour fund offering money to players who "positively move the needle" by generating coverage for the sport?

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Big trouble for leader Brooks Koepka who went waaaaaay left on the par three third.

I mean, if you're playing your local course, you're taking a drop straight away. It's virtually in a forest.

Justin Thomas fires his tee shot into a bunch of spectators too. Both would love those shots back.

Phil Mickelson is on the first hole and he hits a wonderful draw into the green with his second shot, the ball landing pin-high and skipping 15 feet past the hole. As we've already seen today though, that's going to be one heck of a quick putt coming back down the hill.

Xander Schauffele is a fraction short of the green but his third will at least be uphill so he can attack it a little more.

Brooks Koepka, 2017 and 2018 US Open champion, is having a faultless opening couple of hours.

Accurate off the tee and with the putter, he's just tucked home his latest birdie opportunity and that's the outright lead for the American.

Wonder what Bryson DeChambeau makes of it...

Matt Wolff's resurgence is continuing. A seven-foot birdie putt on the second is a third in succession and lifts him back up to two under for his round.

He's had just two pars in his opening 11 holes. Six birdies, two bogeys and a double bogey account for the other nine.

Tommy Fleetwood has started the back nine with two pars.

Phil Mickelson has a ridge to putt over on the 18th green. He gives it a decent thwack, out to the right of the hole. The ball doesn't borrow back though and comes to a stop about six feet past. Birdie try for Mickelson, stays up. Par.

That's got to go down as a missed opportunity for Xander Schauffele though. His eagle putt stays on the green. Birdie it is though and a share of the lead.

American Patrick Rodgers has slogged his way up to the top of the leaderboard.

The 28-year-old birdied the first and fifth and has just shaved another shot off his score on the 12th to join compatriots Russell Henley and Brooks Koepka on three under.

Brooks Koepka cannot put a foot wrong so far. Bogey-free over his front nine, he lands a beautiful tee shot straight down the middle of the par four second hole.

Collin Morikawa and Justin Thomas have both been more wayward - in general and on this hole. Morikawa finds some sand, Thomas the rough.

Xander Schauffele is a local boy and he's delighting the spectators at Torrey Pines so far. From 230 yards out he flies his second on the par-five 18th into the heart of the green and the ball releases up to finish pin-high, about 10 feet to the right. Big eagle chance coming up.

Phil Mickelson, from slightly further out, is slightly further right with his approach, the ball bouncing back off the collar of rough surrounding the green to leave him with a snaking 50 footer.

Gary Woodland is wearing the most garish top we've seen so far today - like something you'd normally see on a US player in the Ryder Cup!

But it's been a consistent round so far by the 2019 champion, with the American making par on each hole but for a birdie on the third.

Webb Simpson's has been consistently bad, though, with six birdies on the way out, while Martin Kaymer, also a previous US Open winner, is well off the pace too.

Image source, Reuters

Brooks Koepka misses a tricky downhill chance for the outright lead on the first. It's a par and he stays three under.

Collin Morikawa draws level with Justin Thomas - who has just signed for his 10th successive par - by following up his eagle at the 18th with a nice birdie.

Tommy Fleetwood is not getting too much television coverage this evening, which is a shame, seeing as how he's just one off the lead after a third birdie of the day on the par-five 18th.

He's playing with American Matt Wolff who was the early leader after three birdies in his opening five holes. He gave all those shots back and more with a bogey-double bogey-bogey run in three holes from the sixth. A birdie on the 18th and another on the first has got him back under par though.

Justin Thomas is a frustrated man - he leaves his approach to the 440-yard first short and faces a tough two shots to rescue par from out of the rough.

Co-leader Brooks Koepka and Collin Morikawa show him how it's done, nicely on the green. Morikawa has a great birdie chance to go from three over to level par within two holes.

That nine footer for birdie was never anywhere but right in the middle of the hole and Phil Mickelson, with the par-five 18th up next to complete his first nine holes, is suddenly in a much better place.

Xander Schauffele, from the back edge, has trundled his ball down to a couple of feet for a scrambling par.