Second round leaderboard (US unless stated):
-9 L Westwood (Eng), G Willis -8 C Hoffman -7 R Karlsson (Swe), R Garrigus -6 L Janzen, S Micheel, T Petrovic, DJ Trahan
Selected others: -5 R McIlroy (NI)-1 P Harrington (Ire)
Westwood scored a course-record 63 in the first round in Memphis
England's Lee Westwood birdied the last three holes for a 68 and a share of the halfway lead at the St Jude Classic.
The world number three, who led overnight, struggled in the blustery conditions and bogeys at eight and 14 dropped him back before his late surge.
Westwood said: "It was tricky. The wind got up and it was gusty, so quite hard to judge. It was a day of patience and I was rewarded with three birdies."
American Garrett Willis shot a 65 to join Westwood on nine under par.
Westwood and Willis are one shot clear of Charley Hoffman, who also carded a five-under-par 65.
England's number one, who is looking for his first win in the United States since 1998, added: "I wasn't missing the fairways by a long way, just on the edge.
"But you've got to be on the fairway to attack the flags, and I just didn't hit it close enough to the flag early on.
"When I bogeyed 14, I stood on the 15th tee and set myself a little task of trying to birdie two of the last four holes to shoot under 70.
"I birdied the last three holes, and I had a chance at 15, too. I'm pleased with that. It's a great way to finish off the day. It sends you into Saturday with momentum."
Sweden's Robert Karlsson is two shots behind Westwood after following his opening 67 with a 66, while Northern Ireland's Rory McIlroy carded his second bogey-free round, moving up to a tie for 10th on five under with a four-under-par 66.
Ireland's Padraig Harrington failed to capitalise on his opening 65 with a 74 to fall back to one under par.
World number five Ian Poulter, who had been three under after the first nine holes of the tournament, missed the cut after shooting a second 72 to lie four over.