Day with a nice wedge into the 13th, another putting contest with McIlroy. As I write there are 31 players within five shots of the lead - if they're not too nasty with the pin positions tomorrow, any one of them could still win this. McIlroy misses that birdie putt, lips out, and he's in danger of being swallowed up down the back nine. Day makes his birdie putt to join a four-way tie for the lead, Stenson birdies 17 to get back to eight under.

Fowler for birdie on 14 and the outright lead... hits it too hard, stays 10 under. Ilonen with a chance to join the lead but his birdie putt on 14 stays a whisker left. McIlroy on tee at 12, going with iron. Nailed it. Palmer at the short 14th, right at the pin, right in the bunker. McIlroy at 13, leaves himself an eight-footer for birdie. Mickelson in with back-to-back birdies at 14 and 15, he's two off the lead.

Iain Carter
BBC Sport's golf correspondent at Valhalla

Rory's irritated, he's angry, he's dropped a shot and he's no longer the outright leader. He's showing signs of his anger and we didn't see much of that at the Open.

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Westwood for a bird on 17, leaves it a couple of feet right. Ilonen on tee at the par-three 14th and that's spot-on, despite his flinch after he hit it.

McIlroy almost sinks his fourth but that's a shot gone and he drops back into a share of the lead with Fowler and Palmer. The not-so-wee man any more rams his putter into this bag and curses and hopes for better things on the 13th. Day makes par, stays -9.

Jason Day very nearly chips in at 12 but he's got a knee-knocker coming back for par. McIlroy has fluffed his effort, he's not in complete control at the moment...

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Rory on 12, from a similar spot to Day... tries to draw it round the trees but gets a flyer and overcooks it. Oosthuizen for eagle at 18, leaves himself a six-footer for birdie and a round of 66. Makes it, he has the clubhouse lead on nine under. Mickelson drains a longun on 14 to stop the bleeding and get back to -7...

McIlroy on the 12th tee and he's tugged another three wood. Day going with two iron and he's done the same. No great drama, but could have done without it. Ilonen on 13, right into the heart with a wedge. Here's Day with his second on 12, 207 yards off a down-slope, six iron... leaked it right, predictably...

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Wales' Jamie Donaldson, who carded a 66 to move within two shots of the lead at eight under, on Sky Sports: "On the 18th, my second shot out of the bunker gave me an eagle putt. I had about 240 yards to carry, I had to cut it and it came out perfectly.

"I misread the eagle putt, I didn't give it enough break. I putted well from long range but I missed a couple of short ones. But I had a good day and I played well."

Lovely chip from McIlroy, should save par from there. It's a five-footer and he sticks it straight down the pipe to stay one shot clear. Stenson nails a long-range bogey putt at 15 but drops to seven under. Par for Day on 11, he stays -9; Westwood drops to -6 after a bogey at 16.

Fowler leaves his 20-footer just right of the cup at 12, taps in for par to stay one behind McIlroy, who is in a spot of bother on 11. Former Open champion Louis Oosthuizen has flown under the radar to within three of the lead, he's three under for his round through 17.

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Furyk for birdie at 11, leaves it short and stays two off the lead. Fowler with the ball below his feet at 12, sweeps it onto the dancefloor. Rory tugs his tee shot left of the green at 11, will need some smart up and down work to save par. Day safely into the heart...

McIlroy makes a fine birdie at 10, his ball having a look before dropping in - he regains the outright lead on -11. Wiesberger birdies 12 to move to -9, Mickelson drops two in a row to drop to -6. Day can only make par, stays -9. Palmer joins a tie for second with a long birdie putt at 11...

McIlroy with his third at 10, leaves himself a makeable uphill putt for birdie. Day chipping from green-side fluff, that's cute as a button, six-footer for birdie. Palmer with his tee shot at 11 and he pushes it a touch right. Stenson rams home a par putt at 14 to stay -8.

Bubba Watson came in for criticism with his on-course swearing on Friday and although the Masters champion fared no better today with a 73, +2 overall and three shots off last place, the American was thankful for the harsh words.

The twice major winner on Twitter:, external "Thanks to everyone for holding me accountable for my actions, it's helping me to get better! #Thanks #Blessed."

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Day going with three wood into 10 and it comes up just short, should get up and down for birdie. McIlroy laying up instead, opting not to go with a long stick, has produced a few iffy shots from the fairway. First-round leader Kevin Chappell is going nowhere, he carded a blemish-free 67 today and is three off the lead.

Westwood firing over the water at 15, right into the guts of the green, birdie chance. Don't write Lee off. Ryan Palmer putting for birdie at 10... leaves it just left, stays -9. Fowler chipping at 11, decent enough, should make par. Ernie Els finishd with a 68, he's five under and in the mixer. Par for Furyk on 10, he stays nine under.

Westwood birdies 14 to get back to -7, this is turning into a right old smash-up, anyone in the top 20 could win this at the moment. Day and McIlroy tonk drives down the middle at 10, Mickelson lets a shot go at 11 to move to -7. Fowler on tee at 11, going with six iron... pushes it slightly, putting from the apron.

He started the day two clear and after thumping one into the drink on four, Rory McIlroy turns having seen his advantage eroded.

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He now shares the lead with Rickie Fowler.