(Reuters) - England's Matthew Fitzpatrick stormed to the second-round clubhouse lead as overnight pacesetter Jon Rahm stalled his engine at the WGC-St. Jude Invitational in Memphis on Friday.
Fitzpatrick birdied the first four holes en route to a six-under-par 64 at TPC Southwind, his career-best score in a PGA Tour-sanctioned event.
The former U.S. amateur champion posted a nine-under 131 halfway total, while world number one Brooks Koepka was four shots behind after a 67.
Rahm was battling at six-under after dropping two shots in 13 holes.
The Spaniard was unable to replicate the hot form on the greens that he displayed on Thursday, when he sank five putts from outside 15 feet.
Sixty-three players are contesting the World Golf Championships event, which has replaced the old PGA Tour event in Memphis.
The time slot, a week after the British Open, prompted five exempt players to decline participation -- Tiger Woods, Francesco Molinari, Rickie Fowler, Bernd Wiesberger and Open champion Shane Lowry.
(Reporting by Andrew Both in Cary, North Carolina; Editing by Christian Radnedge)