Walker at the par-four 11th, going with hybrid, lovely shot, over the corner of the trees. Matsuyama with yet another look at 14 and again it just misses, the man from Japan stays eight under. Kaymer picks up a shot at 12, moves to -6, Stenson makes par, stays -10.

Daniel Summerhays follows birdie at 15 with another at 16, is now nine under. Day for a birdie at 11, from about 12 feet... nailed it, cuts the lead to one again... 

Image source, EPA

Jay Townsend
BBC Radio 5 live at Baltusrol

When a good sand player walks into the bunker and sees that shot, he would be disappointed not leave a tap in.

For the average player, it looks difficult, for these guys it's bread and butter.

Day on tee at the par-four 11th and he rattles one down there with an iron. Kaymer at the par-three 12th, and he's almost stuck it in, a two-footer for birdie. Stenson, however, is a club short. Matsuyama at 14, and he almost spins it back into the hole. Unbelievable! Walker splashes in from a greenside bunker at 10, moves two clear of Day and Stenson...

Image source, AP

-11 Walker (9); -10 Stenson (11), Day (10); -9 Grace (18); -8 Summerhayes (15), Matsuyama (13), Koepka (11), Streb (9).

Selected others:-7 Hatton (18), Casey (18); -6 Harrington (18); -5 Spieth (14), Scott (14); -3 Mickelson (18); -2 Fisher (18); -1 Sullivan (18); +1 Johnston (18); +5 Willett (18); +7 Westwood (18).

Jay Townsend
BBC Radio 5 live at Baltusrol

I am not sure nine more pars will be enough for Jimmy Walker.

Walker makes another save and he's out in nine straight pars. Streb makes birdie, though, to get to eight under. Day makes par at 10, stays one back. Kaymer lips out at 11, stays -5. Summerhays has birdied 15 and is three shots back... bubbling up nicely.

Hoards gathering in front of the clubhouse, as we go back to Walker with a long putt for birdie at nine. He's got another knee-knocker for par, as Stenson tugs his approach left at 11. Magnificent, though, from playing partner Kaymer. Good to see two Englishmen in the top 10, Hatton and Casey both in with seven under. What a chip from Stenson, out of the rough, tap in for par...

Image source, Getty Images

Stenson safely away at the 11th, Walker with a safe tee shot at nine, but nothing spectacular. Streb's tee shot, however, was a beauty, he's got a short one to get to eight under. Koepka with a great bogey putt at 11, only drops to -8. Day at 10, middle of the fairway, a club short. 

Day rattles one down there with an iron at 10, he's hit that a mile. It's all unravelling for Koepka on 11, Matsuyama misses his birdie attempt at 12, stays three off the lead. 

Day for a bird at nine, only a three-footer, and in it pours. Day one behind Walker, who's left himself a knee-knocker at eight... Stenson doesn't hit his birdie putt at 10, stays 10 under. Walker makes par...

Image source, EPA

Jason Day on tee at the par-three ninth... what a shot, stiffed it to four or five feet. That to get to within one of the lead. Walker back on eight, nine into the green, pretty ordinary. Matsuyama at 12, chance of a second straight birdie... Stenson at 10 and he's stiffed one to within six feet. The spurs are jingle-jangling. Here's Brooks Koepka trying to thread one through the trees at 11... CLONK!

Oh hello. Back-to-back birdies for Daniel Summerhays and he's on -8 now after playing 13. A late challenge on the cards?

Japan's Hideki Matsuyama joins Summerhays on -8 with a birdie on 11. Leaderboard starting to take shape now.

Brook Koepka with a confident putting stroke on the 10th to stay on -9.  

Image source, AP

How many lengthy putts have we seen come up short today? Just about every single one. Branden Grace's birdie attempt on the last does not disappoint, apart from perhaps the South African.

Still, we have a new target for the leaders to aim at. A three-under 67 and nine under total that could have been at least three shots better given the putts he missed.

Well done Jimmy Walker, downs his putt for par on the seventh to maintain his one-shot lead over Henrik Stenson. He smiles as it went in off the left side of the hole because any more pace on it would have kept it out.

Jason Day holds himself together at the eighth to stay two shots behind the leader.

Lovely recover from Jimmy Walker on the seventh, leaving himself a manageable putt for par from around six feet out.

Jason Day was in the bunker on the eighth, and he's not too happy after sand-wedging his way out of it.

Branden Grace's challenge drowns in the lake to the left of the 18th fairway.

The South African missed a birdie putt on the 17th and chasing an eagle at the par-five last to set a challenging clubhouse score, tugged his drive.

He pummels his third onto the green but he needs to sink a 50-footer to get to 10 under and you get the feeling even that would be a couple of shots shy.

Jimmy Walker hangs his head, his ball had disappeared into the thick stuff off the left of the seventh green. He's got work to do from there if he is to keep his lead.

Meanwhile, Daniel Summerhayes picks up a shot on the 12th with a huge putt and goes to -7.

Jason Day's putt on the seventh, rolls past the hole and down the hill. It's going to be a rather uneasy one for par, one you can miss if you twitch on it. No problems for the world number one though.

Image source, Getty Images

Paul Casey's eagle putt on 18 doesn't trouble the hole but he's left himself a tap-in birdie and that's a three-under 67 to finish on seven under, alongside fellow Englishman Tyrrell Hatton. 

A good week for the world number 30, who is not eligible for the Ryder Cup later this year because he gave up his European Tour membership.

Wales' Jamie Donaldson is the only man who can challenge their hopes of being the top British players. Donaldson has just birdied the 10th to get to three under.