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From one quality American name to another... Cody Gribble is having a quietly good round to leave him two under with one to play. As it stands, the 24-year-old Texan is joint third. Not bad at all from a man ranked 589th in the world.

John McEnerney: Chambers "of horrors" Bay, should have a sign "abandon hope all ye who enter here" on the gate. Leftys wedge to break the duck!

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As if Tiger Woods didn't have enough to worry about, he's had to cope with the fact that the youngest qualifier for the US Open, 15-year-old Texan Cole Hammer, admitted to reporters that his earliest golfing memory was the 39-year-old's victory at Torrey Pines in 2008 - the last of his 14 majors.

Hammer has the honour of being the first player born this century to compete in a major. So young. So talented. I hate him.

The youth's first nine holes contained two bogeys to leave him two over.

Mickelson drops one from six feet to claim another par at 16. He has dropped further off the lead, though, because Dustin Johnson has gone to five-under with back-to-back birdies. A putt from 12 feet at the fifth keeps the momentum going.

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McIlroy misses his birdie putt at his 12th hole - it was a sinkable one as well from about eight feet. He has to settle for a par to remain evens.

-4 D Johnson 13

-3 P Reed 12

-2 C Gribble 16, K Chappell 14, H Matsuyama (Jpn) 14, M Kuchar 14

Selected:

-1 P Mickelson 15, A Scott (Aus) 13, C Montgomerie (Sco) 12

Level R McIlroy (NI) 13

Bubba fails with his 10-foot putt at the 16th, which swings but too much. He'll have another go for par. Mickelson goes for birdie from 20 feet at the same hole. He gives it a chance with the speed but the direction is just off and he rolls a tad past.

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They don't do short trains in these parts. A big freight mother makes its way along the side of the course, dragging a seemingly endless string of red metal containers as Bubba Watson chips his second at the 16th to about 10 feet short.

Rory McIlroy at four. Lovely iron shot to trickle close to the hole. He'll have eight or so feet for a birdie.

Carl Longhorn: Absolutely loving the golf course and the challenge it is presenting the players, it's going to be four exciting days.

Dustin Johnson leads. He sinks a 10-footer at the fourth for a birdie that sends him four under.

Meanwhile, at the 11th, Marc Warren is a whisper away from moving back to two under as his mid-range putt sneaks by.

Monty is loving this. His second shot at the 12th (after laying up with his drive) bounces once and grips the green to leave him just a few feet away and with a birdie on offer.

Ian Poulter was glowing in his praise of amateur Sam Horsfield earlier in the week. The English teenager has had an up and down first nine (literally considering this course). A double bogey and bogey in his first three holes was not the best start but two birdies mopped up some of the damage. He has just bogeyed the 18th, though, to leave him two-over.

Scotland's Marc Warren had a cracking front nine, picking up two birdies. But he has just dropped his first shot, at the par-four tenth to leave him one-under and level with Colin Montgomerie as leading Brit.

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At the Masters, all the talk was of Rory McIlroy's chances of completing a career grand slam. At the US Open, it is Phil Mickelson's turn to field questions about his potential completing of the major set.

Mickelson has won three of the four majors - the Masters three times as well as the Open (2013) and the PGA (2005) - with the hole in his trophy cabinet reserved for his home Open, a championship in which he has finished runner-up on six occasions.

For more on Mickelson's challenge at Chambers Bay, read our man Iain Carter's blog. Iain also joined George Riley top record a special preview podcast ahead of the tournament, where they discuss all the main challengers and the course.

We now have a four-way tie at the top of the leaderboard, with Patrick Reed now on three-under alongside fellow Americans Matt Kuchar, Kevin Chappell and Dustin Johnson. Two bogeys on the bounce means Mickelson drops to one-under.

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Suddenly things have taken a turn for the chaotic at the top of the leaderboard. I've already documented some of Mickelson's woes at the 14th. Patrick Reed is also struggling, not with the sand but the slope at the first. The two of them look set to drop a couple of shots each but both sink important putts to limit the damage.

Meanwhile, Colin Montgomerie is enjoying himself. He has just birdied the 11th to go one under.

Some big names have already headed out on to the course for their first round, but here are some of the players (and their tee times - in BST) you may want to keep across (nationality is US unless stated)...

1st tee

21:33: Geoff Ogilvy (Aus); Ernie Els (SA); Retief Goosen (SA) 22:17: Jordan Spieth; Jason Day (Aus); Justin Rose (Eng) 22:28: Tiger Woods; Rickie Fowler; Louis Oosthuizen (SA) 22:39: Jimmy Walker; Zach Johnson; Ian Poulter (Eng)

10th tee

22:17: Billy Horschel; Paul Casey (Eng); Lee Westwood (Eng) 21:22: Ryo Ishikawa (Jpn); Luke Donald (Eng); JB Holmes 22:28: Bill Haas; Charl Schwartzel (SA); Hunter Mahan

These bunkers are unforgiving. Huge and unforgiving. And the very antithesis of the white sand of Augusta. Mickelson has a swine of a position as well, on the edge and impeded by the long grass in front. As a left-hander he has a stance but not much of a view to attack. He takes a full swing and gets out but straight in to another huge sand trap further down the hole. Ugly.

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Mickelson stands on the par-four 14th tee, staring down into a bunker wonderland in front of him. And for the second hole running, he finds the sand.

Meanwhile, Dustin Johnson has a 15-footer at the second for birdie but misses right. A par keeps him on three-under.

So, what are your early impressions of Chambers Bay? Who has impressed you so far? And who do think will tackle the course and conditions best over the next four days?

You can send your thoughts via Twitter, using the hashtag #bbcgolf, or text on 81111 (UK only).