And now it's world number two Justin Thomas applying the pressure!

First birdie on the back nine for the American, it moves him to nine under par and within two strokes of the lead.

Long eagle putt for Adam Scott at the 17th, it puts the brakes on a little prematurely, but the Australian will fancy his chances of prodding this in for birdie.

A quick flick through the book, and in he rolls it. He's just one off the lead...

Image source, Getty Images

Things have suddenly concertinaed at the top of the leaderboard, with Brooks Koepka being reeled back in a touch by those in the chasing pack.

Three at nine under, but Rickie Fowler misses the chance to join them as he stings a birdie putt wide at the par-three 16th.

It keeps him among a group of five players a stroke further back.

Tiger Woods had mixed emotions after his four-under 66: "It is good but I'm also disappointed at the same time.

"For 29 holes I made three bogeys and played pretty clean - two of those were three putts. I played better than my score indicates.

"I wish my score was closer to the lead but not many guys are up there. This golf course is very gettable.

"That front nine was like everyone was making birdies and you could hear roar after roar and I think it will be the same tomorrow.

"I think Brooks will add to his total so that would put me five or six behind so I'd have to go out and shoot low.

"We have to be aggressive, pars just won't be enough."

Image source, Getty Images

Image source, Getty Images

England's Matt Wallace produced one of the most memorable moments of the tournament when he aced the 16th and one word immediately sprung to mind...

"Mindblowing!" says the 28-year-old from Hillingdon.

"To hole in one on a Saturday at a major was really special. I enjoyed every minute.

"I will remember this forever. It was the best round of golf ever, so enjoyable playing with Jordan Spieth and Andrew Putnam.

"I said to my caddie a couple of holes before it was the most fun I'd ever had and then that happened. It was mental."

Adam Scott is now within two strokes of the lead after a birdie at 16, immediately wiping out that dropped shot a hole earlier.

And now it's a three-way tie for second place... Jon Rahm sinks his putt at the par-five 17th to make it back-to-back birdies for the Spaniard.

Game on...

Alex Miceli
US golf reporter on BBC Radio 5 live

If you came here on Thursday morning and had to write up a top-10 leaderboard, you'd be pretty close to how it looks right now. You'd maybe only add Rory McIlroy and Jordan Spieth.

How about that from Brandon Stone!

The South African almost slam dunks his tee shot straight into the cup at the par-three 16th, but instead leaves a huge divot right next to the cup and the hole is having to be re-cut...

Wonderful recovery from the rough cupping the bank below the 15th green, deft hands from the big man Brooks Koepka.

This putt to escape with just the one dropped shot... and he sinks it. His lead stood at five shots two holes ago, now it's back to two.

Tommy Fleetwood signs for a one-under 69 to leave him two under for the tournament - but says it could have been so much better.

"I played pretty good to be fair, but the last couple of days just hasn't happened on the greens which is frustrating. I have got so little out of two rounds," he said.

"The course has played pretty fair and there is a score out there but I'm not the one who has done it. Tomorrow I have to wait for another chance.

"The loud cheers can be heard across the course - it's just frustrating that I can't do it and I have to hear everyone else do it. I'd like to be the one they're cheering. But it's great for golf and enjoyable. It makes golf better.

"It'll be a good effort to get anywhere near tomorrow, I've just got to go out and do the best I can. I'd think I'm too far back, but you never know."

Are the nerves getting to Brooks Koepka? Flawless through 13 holes today, but a bogey at the last and now he's nestled up against a tree... finally one of those big drives goes awry.

He's having to take a penalty drop. Now don't get this wrong, Brooks.

He stings it long and left, sending spectators sprawling like he's the don and he's asking them to dance.

Image source, Getty Images

Alex Miceli
US golf reporter on BBC Radio 5 live

Tiger has played the front nine in 10 under this week, he's played the back nine at two over par. He's going to go home tonight and he's got to try and work out how he can play this back nine under par. He cannot win this golf tournament playing over par on the back nine.

Solemn slope over to his ball for Rickie Fowler, the putts are just not dropping for the American at the minute and he's all frowns beneath the meaty peak of his baseball cap.

Two bogeys on the back nine for the American, who sees his birdie putt come up short at 15.

Image source, Getty Images

Nope, not happening. Woods' putt holds his line on the left, refusing to budge for a birdie. Five birdies on the front nine, none on the back, leaves Woods signing for a four-under 66.

That gives him the clubhouse lead alongside playing partner Stewart Cink, but both are trailing Brooks Koepka by a considerable margin.

-12 B Koepka (14)

-9 G Woodland (14)

Selected others

-8 T Woods (F) S Cink (F) J Thomas (15) A Scott (15) R Fowler (14) J Rahm (16)

-5 E Pepperell (F*) I Poulter (F) M Wallace (F) J Rose (17)

-2 R McIlroy (F)

Tiger Woods has been impeccable tee to green. But his putter has not been his friend on the back nine.

He has another chance for a birdie on the last, whoops of support as his name is introduced by a man with a loudspeaker on the final green. Don't think I've ever seen that before?

Camera phones out at the ready as Tiger skulks around this 15-foot putt...

Image source, Reuters

England's Ian Poulter is five under for the tournament after following his delayed second round this morning with a two-under 68 in the afternoon: "It was pretty tough, it was a long day.

"When you set an alarm clock at 4:30am and know how hot and humid it was going to be - that was the most difficult thing.

"You could be aggressive and make birdies but obviously guys in front are making more than me.

"I would expecte Brooks to finish 13 or 14 under so I'm going to be way back. I need to play well, conserve some energy tonight and come out as strong as I possibly can."

STOP THE PRESS.

A first bogey in 44 holes for leader Brooks Koepka.

The American undercooks his par putt so badly it comes off his flat iron blue, and he has to scuttle over and prod it in for a bogey that brings him back to 12 under par.

Gary Woodland, from a similar distance, rolls in for a well-made birdie to go into outright second.

Just the three-shot lead now...

Jordan Spieth has just tapped in for a one-under 69 and is at four under for the championship. He had a triple-bogey seven on the 12th which knocked him back from seven under and he could only muster one birdie, after a bogey on the run-in.

Image source, Getty Images

Talking of the chasers... he comes Jon Rahm. Superb birdie putt at 16 for the Spaniard as he walks it in from long range to move to eight under par.