Palmer overcooks his approach at 17, Wiesberger almost holes his chip at 18. He'll tap that in for a round of 65 and the joint lead, with McIlroy, on -12. That's also the joint best of the day with Hunter Mahan. Mickelson almost holed his monster but taps in for birdie for a round of 67 and 10 under.

Iain Carter
BBC Sport's golf correspondent at Valhalla

"The standard of the majors this year has been as good as any for a long time. There hasn't been a duff one all year."

Hard to disagree. The supremely talented Bubba Watson clinched a second Masters title in April, Martin Kaymer notched up his second major with a masterful display at the US Open in June and Rory McIlroy landed a first Open title last month in thrilling fashion.

Mickelson hits a glorious hybrid into the 18th, he's got a monster uphill for eagle. Wiesberger with a poor swing but if he gets up and down from there, that's still a birdie. McIlroy pops in for birdie on 16, grabs the outright lead on 12 under.

Jay Townsend
Former European Tour golfer on BBC Radio 5 live

Bernd Wiesberger's not afraid to win I can tell you that. I saw him decimate the field in Korea.

The Austrian won his first European Tour title by five shots in 2012.

Wiesberger gets chocs away down the 18th, Mickelson pushes his drive right into the short rough. Fowler makes par at 17, he stays one off the lead, although that's about to be two. Day has plenty to do to make par after his third...

Palmer leaves his birdie putt left of the hole at 16 but taps in to stay one off the lead. Day has got 255 yards to go at 16 and he's going with an iron. Comes up short, maybe should have gone with the old hybrid. McIlroy is slap-bang in the middle of the fairway, he's only got a nine iron - you have to say that's magnificent, stiffs it to two feet. That for the outright lead...

Palmer into 16, from 190 yards, he's got a 12-footer for birdie. Ilonen with a blind second into 17 and that's not half bad, just a touch long. McIlroy slaps another beauty down the middle at 16, Day is in Robin Hood country... but gets a lucky bounce out...

Mickelson only makes par at 17 to stay nine under but he and Wiesberger have got eagle chances at 18 and should make birdies if they get their drives away.

DeLaet for birdie at 18 and he's missed that by the width of a fag paper, that's a round of 68 for the Canadian for eight under. Lordy, lordy, look at this from Wiesberger - he's stuck his second on 17 to within six inches of the hole and will nick the outright lead on 11 under... SCRATCH THAT! McIlroy joins him on 11 under with a 12-foot birdie putt at 15... Day misses his, stays -10...

Steve Stricker could be playing his way into Tom Watson's Ryder Cup team - currently a US vice-captain, he's birdied 16 to get to seven under par. Jason Day and McIlroy safely on in two at 15, chances for birdies and the outright lead...

Image source, PA

Graeme McDowell, Europe's Ryder Cup hero in 2010, says he has no doubts over his place on the team for Gleneagles next month.

"I want to be in the automatic spots if I can. I'll be out there all guns blazing tomorrow and Ryder Cup is of course very important to me," McDowell tells BBC Radio 5 Live.

"I'm not uncomfortable. I'm optimistic about the way I'm playing, I'm optimistic about finishing in the automatic spots and I'm optimistic about a pick. I hope to be there in some shape or form. I've showed the captain I'm playing well, so I'll keep some energy in the tank and hopefully get the call up."

McDowell is currently in the team via the world points list, though Luke Donald and Stephen Gallacher are hunting the Northern Irishman and Jamie Donaldson, currently the final two in the nine automatic places.

England's Chris Wood tweets:, external Played better than -1 today. Course was a little wet! There's a score out there for me tomorrow...

Wood, from Bristol, is four under for the championship.

Ilonen playing into 16 and it comes up short and rolls away. Stenson up the hill for eagle at the last... drifts right but that's a round of 67 for -9 and a share of the clubhouse lead.

Image source, EPA

Bernd Wiesberger has not been overawed by playing in the company of Mickelson today, he's just knocked in a birdie on 16 to make it a five-way tie for the lead. McIlroy saves par at 14, stays -10, as does Day. Water down the right on 15 and Day finds sand off the tee. McIlroy going with the big boy and that's a monster...

PGA professional Graham Fox tweets:, external I thought golf was hard until I delivered my baby girl on the bathroom floor today all by myself. Claire was immense. I was sweating bullets.

Canada's Graham DeLaet has been flying under the radar all week but he's just birdied 16 to get to eight under. Mickelson makes that birdie at 16, he's now nine under, one off the lead and hurtling towards the clubhouse like a man on fire.

Mickelson has got things going on and here he is with a crackerjack approach at 16, chance for a third straight birdie. Westwood makes the most of a fine bunker shot at 18, popping in for birdie, a round of 69 and -7 overall. He's not out of this by any means.

Image source, Getty Images

Ilonen on 15, 173 to the flag, safe as houses. Day on tee at the 204-yard 14th... all over the pin and 15 fete past. Fowler for birdie at 15, leaves it a touch left, stays -10. McIlroy struggling to hold this together at the moment, he's tugged his tee shot left at 14.

John McEnerney:, external Turning out to be a cracker of a Major, Top players playing some top golf also making mistakes which is keeping it interesting!

The Pete:, external I'm trying to think of a sportsman and a phrase more associated than Lee Westwood and 'good putt, just missed'. Is there one?

Lee Cattermole, yellow card?