James Bamford: , externalWell done @usopengolf taking the pros out of their comfort zone and challenging them. Majors are supposed to be hard!

Image source, EPA

Dustin Johnson mullers his drive on the 500-yard par-four seventh. It finishes on an upslope which is so dry that the ball starts wandering back towards the tee. It's not all bad for DJ - he's got no more than a 9-iron left.

Rory McIlroy fires pin-high on the sixth - he needs a birdie or two to ease his cut nerves.

Another shot gone for Henrik Stenson at the 15th and he is two over after six, three under for the tournament. Dustin Johnson in for par on six to stay one one behind Patrick Reed who slides in from a yard on the fifth to stay six under.

Mickelson wanders over to the first tee. It's playing as a par-five today remember. He's drilled a three-wood down the middle. He needs a solid back nine just to make sure he's here for the weekend, never mind trying to wrap up his career grand slam.

Image source, EPA

"I wanted to shoot five or six today," said Tiger Woods after he bowed out of the tournament today, finishing well off the pace on +16.

"I wanted to be on the other side of it. I hit a little bit better today, but again, I made nothing.

I didn't make any putts the first two days.

"I just continue practicing, continue working on it. And hopefully it will be a little bit better."

Andy, Armagh: Dustin Johnson's length off the tee gives him a huge advantage this week at this very long Chambers Bay course. However, the problem with him is that he always has a potential double or triple bogey in him on each round.

To win a major championship at this level with this sort of company on the leaderboard he can't afford to let that happen. Four solid rounds are needed, but Dustin Johnson rarely delivers that.

Dustin Johnson out of the rough on the sixth and straight into sand.

Colin Montgomerie is hunched over his par putt on the 14th but he's back to level after a second successive bogey.

We've not seen much of Bubba Watson - chiefly because he's had three bogeys and dropped out to +3. But here he is on the 18th, his ninth, rolling in a birdie. He is playing with Phil Mickelson who has had a troubling nine holes. Another shot slips away on the 18th and he is back to +2.

Image source, Getty Images

Henrik Stenson is on the par-three 15th, the downhill hole towards the sea and that would have looked great in the air. Straight at the flag. But it is fractionally short and starts rolling back towards the sand. It stays out of the bunker but rather than having a 10-footer for birdie, it's more like 40.

Patrick Reed takes the lead out to six under. The American has had a blistering start with two birdies in his opening four holes.

From the slate grey sand, Rory splashes out with a pitch and run shot that wanders towards the hole and comes to rest a couple of inches to the right. Terrific effort.

Here's Monty on the 14th, up and across the green - I say green, it's more of a sandy brown - and that is rolling eight feet past.

Image source, AP

Justin Rose was in the same playing group as Jason Day, who collapsed on his way to the ninth green in an apparent recurrence of vertigo that he has suffered before.

"He seemed chirpy, buoyant all day. That was out of the blue, for sure," said Rose.

"It was a pretty severe bit of hill that he was sitting on. I thought maybe twisted his ankle."

Image source, AP

Rory McIlroy is in the same bunker Dustin Johnson has just left on the par-four fifth. The world number one needs another sand save otherwise he's right on the cut mark, which is currently +3.

A rare mistake from Henrik Stenson on the 14th. His 12-foot par putt pulls up short and he is dropping back to four under.

Australia's Jason Day had a bit of a turn as he was finishing up his round a little earlier. He collapsed on the ninth before receiving medical attention and then getting up to finish his hole and round.

His agent Bud Martin said in a statement: "Jason is being treated on site at Chambers Bay after feeling dizzy near the end of his round. We will provide more information later today after getting through the medical evaluation process. Jason wants to express his appreciation for all the good wishes from so many fans and friends."

Mickelson's 30-foot birdie putt pulls up a couple of inches short, while Dustin Johnson flicks out of the sand on five and has an anxious wait to see if his ball has gone far enough to hold on the green. It does and he's quickly up marking it. He then knocks in the 10-foot par putt.

Back on the fourth, Rory McIlory is up and down from the sand for a par to stay two over but Colin Montgomerie leaves his par-putt short on the 13th to go back to one under.

Straight on to the 17th and Mickelson comes within a whisker of smashing into the pin with his tee shot. I doubt the ball would have dropped had it hit the stick but it gave the crowd reason to "ooh" and "aah".

Henrik Stenson has been in a bit of trouble on the par-four 14th. How do I know? He's facing a wedge to the green for his third shot. He fires straight at the flag and his ball lands and stops 10 feet short.

Image source, Getty Images

Phil Mickelson in for par on 16 after wonderfully creative second shot to the par-four green that landed well short and utilised the humps and bumps to give him a birdie look.

Dustin Johnson comes up a fraction short with his approach on the fifth and that spells trouble. His ball thinks about stopping 20 feet short of the pin but then decides it fancies a wee meander in to the solitary bunker protecting the green. A tough break.

John McEnerney: , externalStenson has got that late 2013 form back again & if that putter stays hot it'll be easier to assemble a Liatorp than 2 catch him

A Liatorp is a particular furniture range at a well-known Swedish flat-pack purveyor in case you were wondering...

Ah, here is John with more information:

John McEnerney:, external "The Liatorp is called the "divorcemaker" by its makers - the most difficult item to assemble"

England's Paul Casey had a one-under 69 today and he is +1 for the tournament.

He told BBC Radio 5 live: "Anytime you break par at the U.S. Open is not bad."

However Casey has been the latest player to criticise the state of the greens at Chambers Bay. "Maybe they are trying to recreate when they played US Opens a hundred years ago!" he said.

"They are not good. It's a very blotchy surface, a very difficult surface to putt on. They are not enjoyable, but it is the same for everybody, so I am trying to embrace it as much as I can. It is what is it. Do we wish we had better playing surfaces? Of course we do."

Image source, Getty Images

Solid start for Sergio Garcia, three pars after a birdie at one and he is one under. Four holes and four pars for Henrik Stenson and that kind of steady play might just be enough to see him retain his share of the lead come the end of play.

Dustin Johnson is back alongside Stenson after knocking a birdie in at the fourth.

That means Monty is the best Brit at Chambers Bay. His fellow Scot Marc Warren, who had a two-under 68 on day one, has had a shocker of an opening. A bogey, double bogey start has seen the 34-year-old drop to one over.