Paul Casey reacts following his second round of the Memorial golf tournament Friday in Dublin, Ohio. Casey shot a 6-under 66 to take a three-stroke lead over Bubba Watson.

DUBLIN, Ohio — There were dark times over the past few years when Paul Casey wondered if maybe he was done with golf.

A painful divorce and a series of painful injuries made Casey, once the No. 3-ranked player in the world, doubt himself and his abilities.

Casey sits atop the lead at the Memorial Tournament, a wiser man with a different perspective.

Casey shot his second 6-under 66 in a row Friday to forge a three-stroke lead over Bubba Watson through 36 holes at Muirfield Village in the tournament founded and hosted by Jack Nicklaus.

Rory McIlroy, who was up by three shots after a glittering 63 in the opening round, had three double-bogeys in a row in a 78 that dropped him all the way into a tie for 24th.