A second consecutive 66 saw Paul Casey take over from Rory McIlroy at the top of the Memorial Tournament presented by Nationwide Insurance leaderboard.
Casey shot a 66 on Thursday to sit in the three-man group immediately behind McIlroy alongside Americans Bubba Watson and Chris Kirk, and he picked up where he left off with an eagle, six birdies and two bogeys.
That left the 36 year old on 12 under for the tournament and with a three shot lead over the rest of the field.
Watson was his nearest challenger, the American carding a 69 on Friday, while Kirk and Martin Flores were one shot further back.
Dane Thorbjørn Olesen was safely inside the top ten on six under after shooting a 67 that included seven birdies and two bogeys.
McIlroy was brought back to earth as he carded a six over par 78.
The Northern Irishman followed up his BMW PGA Championship victory at Wentworth on Sunday with a superb 63 in the first round in Ohio to open up a three shot lead, but had a day to forget on Friday.
Most of the damage was done on the way out 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 tenth, 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.
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.
