England's Paul Casey stormed into a three-shot lead at the Memorial Tournament on a day which saw Rory McIlroy brought crashing back to earth.
Casey's second successive six-under-par round of 66, which included an eagle, six birdies and just the two dropped shots, left him on 12 under for the tournament and with clear daylight to the chasing pack heading into the weekend.
"I was ecstatic with the way I played," Casey said on www.pgatour.com. "There was a couple of mistakes in there but that's Muirfield Village. It's a tricky golf course and you don't need to do a lot wrong to make a mistake."
In second spot, three shots back after a 69 is Bubba Watson, while Chris Kirk is a further shot adrift in third after a second-round 70.
Casey, Watson and Kirk were all joint second following the first day, which was dominated by McIlroy.
The Northern Irishman boasted a three-shot advantage of his own after shooting a brilliant 63 as he continued the form he showed in winning the BMW PGA Championship at Wentworth on Sunday.
However, the 25-year-old had a day to forget on Friday as he carded a six-over-par 78 to tumble down the leaderboard.
Most of the damage was done on a disastrous opening nine where three consecutive double bogeys saw him go out in 43 at Muirfield Village.
Starting on the back nine, McIlroy bogeyed his opening hole, the par-four 10th, before parring 11 and picking the shot back up on 12.
It went rapidly downhill after that, though, as double bogeys followed on 13, 14 and 15 before two pars and a further bogey saw him reach the turn four shots off the lead.
That represented a 12-shot collapse on the back nine from Thursday where he had picked up two eagles, three birdies and a double bogey to record a 31.
McIlroy did manage to turn things round a bit on the back nine, though, picking up birdies on the second and seventh while only dropping the one shot in between as he ended the day on three under par overall.
Despite that partial recovery, McIlroy found himself nine shots behind Casey at the end of the day as the 36-year-old Englishman enjoyed another good round in Ohio.
McIlroy hurt his knee during Thursday's round, but he insisted it did not affect him too badly on Friday.
He said: "T he knee's OK. It was a little bit sore this morning on the range but out on the course it was fine, the painkillers kicked in. I felt it a little bit but it didn't really bother me too much.
"I missed fairways, that was a big thing, I didn't realise how thick the rough was until I got into it today. Obviously that three-hole stretch, 13, 14, 15, didn't help. Take those three holes out of it and it wouldn't actually have been that bad a day.
"It's not disastrous even though I had such a bad day."
After Watson and Kirk, Hideki Matsuyama (67) and Martin Flores (68) were joint fourth on seven under, followed by a group of four on six under - Thorbjorn Olesen, Hunter Mahan, Ryan Moore and Scott Langley.
Justin Rose was among those who failed to make the cut after the former US Open winner added a 72 to his opening-day 73.