Third round leaderboard (US unless stated):
-11 R Garrigus -9 R Karlsson (Swe) -8 H Slocum, L Westwood (Eng) -6 L Janzen, S Micheel, T Petrovic, G Willis
Selected others: -3 R McIlroy (NIre) -2 R Goosen (SA), Level P Harrington (Ire)
Like many others, Westwood struggled to play his best golf in intense heat
Lee Westwood finished three shots off the lead after a day of searing heat in round three of the St Jude Classic.
The British number one, who had shared the overnight lead, returned a one-over-par 71 to stand on eight under overall as Robert Garrigus led.
Despite battling food poisoning, and recording a bogey at the last, Garrigus's 66 saw him lead Robert Karlsson of Sweden by two shots.
Westwood, who led after each of the first two rounds, is tied for third.
The man from Worksop will tee off on Sunday in the penultimate group with Heath Slocum, whose 66 pushed him 12 places up the leaderboard.
Four players are tied for fifth on six under in Memphis, including Garrett Willis, who returned a disappointing 74.
Garrigus said: "Last week I got a bout of food-poisoning and I played seven holes of the US Open qualifiers and felt I had gone five rounds with Mike Tyson.
"I think I've drunk 25 gallons of water this week. It's so hot out there, the bottom of my bag was melting when I put it down on the asphalt path."
Garrigus, 32, has had eight top-10 finishes but never won on the US tour. He has limited playing status on the PGA Tour this season but covered the back nine in just 31 shots.
Karlsson was boosted by a late birdie when he chipped in from just off the 18th green for a 68, but Saturday was all about Garrigus's fine play.
He birdied the 11th and 12th to edge one ahead before rolling in a 20-footer down the hill at the par-four 15th to double his advantage.
At the par-five 16th, Garrigus struck a superb six-iron from 196 yards to five feet to set up an eagle.
Westwood produced an uneven round featuring four bogeys and three birdies. Garrett Willis, who had shared the lead after two rounds with the Englishman, dropped right off the pace after carding a 73.