Delighted Rory out on his own but G-Mac keen to up the ante
Rory McIlroy is threatening to lap the field, but new Ryder Cup vice-captain Graeme McDowell wants to give him "a run for his money" in the $7m (£5.25m) BMW PGA Championship.
As Ulsterman McDowell fired a 67 to get to six-under-par, compatriot McIlroy put on a ball-striking clinic, cruising to a bogey-free 65 to lead the field by three strokes on 12-under.
He played so well that playing partner Alex Noren - a man who closed with a 62 to win last year - described McIlroy's seven-birdie show as "the best round I've ever seen".
And Noren added: "I'm about to quit golf... I think it's hard to draw off it when it's that good.
"It's tough because it's almost like you're trying to play better than you need to when you see that. I really wanted to get the honour and be first on the tee, and then you don't have to hit after that 330-yard driver or 300-yard three-wood."
It's just as well for the rest that Holywood star McIlroy didn't birdie either of the two closing par-fives for the second day running.
Had the 29-year-old birdied just one of them, he'd have matched Paul McGinley's 10-year-old 36-hole scoring record.
"I played really well - bogey-free around here, I think I only missed one green, not by a lot," McIlroy said after he went out in 32 with birdies at the fourth, seventh and ninth, before making another four in a row from the 12th.
"It was one of the best rounds of golf I've played this year, ball-striking-wise."
Frenchman Sebastian Gros (28) shot 66 and English rookie Sam Horsfield (21) a 68 to trail McIlroy by three shots in second, with Englishman Tommy Fleetwood - a man who came from behind to deny the Ulsterman in Abu Dhabi in January - only four behind after a strong 66.
While McIlroy missed chances inside 10ft on the first two greens, he made amends by rolling in a nine-footer at the ninth, a 25-footer at the 13th and a 40-footer at the 15th.
The rest of his birdies all came inside six feet, with the pick of them from around 18 inches at the short 14th.
"I was thinking, 'Here we go'," he confessed with a grin after those two early misses on the greens. "But I played great after that and took my chances when I was hitting good shots."
Having come from behind to win in 2014, he admits that winning from the front would be "a huge confidence boost".
Nobody knows better than McIlroy's former stablemate McDowell that the chasing pack have their work cut out.
"When Rory is on his game, he's incredibly tough to catch," said McDowell, who made seven birdies in a 67 on a rain-softened West Course alongside Ryder Cup captain Thomas Bjorn and a frustrated Shane Lowry.
"But obviously I'm hoping to give him a run for his money this weekend and hopefully we can get some drier weather and a little bit of wind and keep us all honest."
Tied ninth, McDowell says he still wants to make a fifth Ryder Cup appearance but admits that being part of the backroom team has its pluses.
"It's taken the weight off my shoulders a little bit," McDowell said. "I'm out there kind of free-wheeling, enjoying my golf and managing to play well."
No wonder he was tickled to detect the surprised tone in Bjorn's congratulatory 'Nice playing, G-Mac' as they shook hands at the end.
"I'd dearly love to be on the team playing in France, but in the meantime I'm very committed to helping the captain with everything I can do for him," he said.
Lowry is eight shots behind in 30th on four-under after a mediocre 71 but insists he's putting well enough to make up ground.
"I know around here that it doesn't take much to move up the leaderboard," Lowry said. "I have to stay patient and keep playing the way I am."
There's no way back now for Paul Dunne, however, after he double-bogeyed the first and shot 75 to miss the cut by three shots on two-over-par, with Padraig Harrington two shots further back after a 70.
On the Challenge Tour, Gary Hurley shot 70 to be 10 shots behind France's Thomas Linard in the D&D REAL Czech Challenge with Jack Hume and Jonny Caldwell another shot back after 71s.
Justin Rose shot a six-under 64 to take the early lead on 10-under in the PGA Tour's Fort Worth Invitational where Seamus Power was cut on eight-over after a 73.
Brendan McGovern was also cut in the KitchenAid Senior PGA Championship in Michigan, finishing on 13-over after rounds of 78 and 77.
In amateur golf, England's Trevor Foster shot 70 to come from five shots behind to win the Irish Seniors Amateur Open by two strokes on level-par 216 from overnight leader Steve Graham at Concra Wood.