MEMPHIS, June 8, 2013 (AFP) - Stefani, seeking his first US PGA title, fired a four-under par 66 to stand on 12-under 198 after 54 holes, one stroke ahead of countryman Harris English, the 36-hole leader who could only manage a 69 on Saturday at TPC Southwind.
"I've never held a lead going into Sunday," Stefani said. "We pushed each other to play better today. Hopefully we can go out there tomorrow and push each other to make a lot of birdies."
Four-time major champion Phil Mickelson fired a 65 and jumped to a share of sixth on 203, level with fellow American Eric Meierdierks and one back of fellow Americans Patrick Reed, Nicholas Thompson and Scott Stallings.
Ireland's Padraig Harrington also fired a 65 to reach 204 and share eighth with Americans Ryan Palmer and Roberto Castro.
"It's anybody's ball game," English said. "If anybody shoots five-under tomorrow they can move right to the top."
Stefani, whose best PGA showing was a share of seventh at last March's Tampa Bay Championship in only his ninth PGA start, had back-to-back birdies at the second and third and again at the ninth and 10th.
"I was playing so well the first 10 holes and was really feeling comfortable with my swing," Stefani said.
Then came a quadruple-bogey at the par-3 11th after he found the water.
"The quad on 11 was a mis-club and a missed choice in the wind," Stefani said. "I just told myself just keep making good golf swings, keep making opportunities and see what happens.
"After it happened I hit the tee shot on 12 and had pretty much forgotten all about it."
But Stefani answered with a birdie at the par-3 14th and then birdies at the final three holes.
English, also seeking his first PGA title at the $5.7 million event, had a mild day by comparison, opening with a birdie and adding another at the par-5 third, then taking bogeys at the fifth and par-3 eighth before a birdie at 18.
"I kind of hung in there all day," English said. "I was really happy to start off with a birdie. I feel good about my game. And making birdie on 18 really helped me out."
Mickelson had a roller coaster round that included six birdies, including three in the last five holes, plus three bogeys, including one each to open and close the front nine, and an eagle at the par-5 third hole.
Meierdierks, who fired a 66, had a hole-in-one on the eighth.
Leading scores on Saturday after the third round of the $5.7 million US PGA Tour St. Jude Classic (USA unless noted, par-70):
198 - Shawn Stefani 67-65-66
199 - Harris English 66-64-69
202 - Patrick Reed 69-69-64, Nicholas Thompson 67-69-66, Scott Stallings 67-68-67
203 - Phil Mickelson 71-67-65, Eric Meierdierks 68-69-66
204 - Padraig Harrington (IRL) 69-70-65, Ryan Palmer 72-67-65, Roberto Castro 68-69-67
205 - Jonathan Byrd 70-69-66, John Rollins 67-71-67, Ian Poulter (ENG) 69-68-68, Ben Crane 69-68-68, Dustin Johnson 67-70-68, Justin Hicks 67-69-69, Paul Haley 67-68-70
206 - Brandt Jobe 69-71-66, Brendon Todd 69-71-66, John Merrick 69-71-66, Justin Leonard 69-71-66, Kevin Stadler 69-70-67, Nick O'Hern (AUS) 68-71-67, Jim Herman 69-69-68, Charles Howell 71-67-68, Billy Mayfair 68-70-68, Peter Hanson (SWE) 67-71-68, Rory Sabbatini (RSA) 69-69-68, Martin Flores 66-72-68, Camilo Villegas (VEN) 69-68-69, Bob Estes 68-69-69, Chez Reavie 69-68-69, Doug LaBelle 70-66-70, Glen Day 66-70-70