-6 Oosthuizen (10)

-4 Rahm (12), DeChambeau (11), McIlroy (10), Hughes (10)

-3 Koepka (16)

Selected:

-2 Migliozzi (F), Schauffele (14), Morikawa (13)

That is absolutely horrible for Collin Morikawa.

The American was one of those chasing Bryson DeChambeau on four under but he flirts with the rough down the right of the 13th, then overhits into some even nastier grass off the back of the green.

The result: a double bogey and possible end to his hopes.

There's been rattlesnake sightings on the course at Torrey Pines this week and Jon Rahm just had a birdie putt that curled one way and then the other, just like a reptile.

But it stayed inches short of the 12th hole and he stays on four under.

Matthew Wolff, meanwhile, registers a fourth bogey in five holes and his title hopes are over.

Anyone want to see just how close Bryson DeChambeau came to hitting an ace on the par-three eighth? Course you do...

Right. Rory McIlroy has a good run coming up now.

He's birdied the 12th in every round this week and the 13th twice.

And he's just landed his tee shot on the 11th 30ft left of the hole to give himself a birdie chance here too.

Bryson DeChambeau makes his first bogey of the day on the 11th. It's his first bogey of the weekend actually.

He drops out of a share of the lead.

I don't like Brooks Koepka's chances after that late bogey.

He was in the bunker off the 16th tee and the second shot overshot the flag by too much. You would think he'd have to leave Torrey Pines on at least five under to give himself any chance.

Two big holes to go.

Oh my goodness, what a putt.

Louis Oosthuizen puts the disappointment at his approach shot behind him with a simply wonderful putt that tracked all the way. Must have been 25 feet, that.

And with events elsewhere, the South African is two clear at the summit.

How are your scrambling skills Bryson? DeChambeau leaks his tee shot on the 200+ yard par-three 11th out to the right.

The scrambling skills of the spectators are decent though as they jostle to get the best position to watch the reigning champion's second shot.

It's a terrific shot, landing a few feet short of the hole and scuttling maybe 10 past. Big par putt coming up.

Louis Oosthuizen looks crestfallen despite hitting the green in two at 10.

He wanted to be closer to the pin. Birdies on his mind.

And breathe. He's made it!

We've not seen much of Xander Schauffele today but here he is standing over a birdie putt on the long 13th.

I'm going to take a wild guess and say he's going to make this eight-footer.

Ta-da! He's had four top-six finishes in four US Open appearances. That birdie takes him into a share of eighth.

McIlroy chips on to within 8ft on the 10th and has a nervy par putt incoming.

Rory McIlroy was in the rough off the 10th tee and he groans in frustration as he just falls short of the green with his second shot.

If I were him, I'd have been happy to make it over the nasty-looking bunker. I'm not a four-time major champion though I suppose...

Got to be honest, I thought Mackenzie Hughes' race was run when he posted three bogeys in the opening six holes.

But he's bounced back with two birdies including a lovely putt on the par five ninth.

That putt proves a great guide for Louis Oosthuizen, who buries from similar distance to draw level with Bryson DeChambeau at the top of the leaderboard.

What a rollercoaster this is - and we're halfway through, with every player on the back nine now.

Will Bryson DeChambeau respond? No. Two-putt par.

Of course, he won't be aware of what Brooks Koepka has done.

Given the recent history between these two, I wonder if the golfing gods are plotting a play-off?

As Bryson DeChambeau lines up a birdie putt on the 10th, Brooks Koepka makes his on the 15th to get to one off the defending champion's lead.

That is painful.

Rory McIlroy bends double over his putter as the birdie putt slides to the left of the ninth hole. I reckon that's the third birdie chance he's missed today. You don't catch someone of Bryson DeChambeau's calibre like that.

Absorbing.

No one is going to bed are they?

Thumbs up if you're staying up with us? Thumbs down if for some crazy reason you have to go to bed.