Paul Casey expected to be chasing someone at the Memorial on Friday, figuring it would be Rory McIlroy.
After two holes, Casey had the lead to himself at Muirfield Village. He went on to another 6-under 66 to build a three-shot lead over Masters champion Bubba Watson, with McIlroy falling nine shots behind.
Casey was at 12-under 132.
McIlroy opened with a 63 and was 15 shots worse Friday. He didn't blame a sore left knee as much as his inability to hit fairways. He made three straight double bogeys, had a nine-hole score of 40 or worse in his fourth straight PGA Tour event and had a 78.
Watson got within one shot of Casey late in the round until closing with back-to-back bogeys for a 69.