Norton - Australian Adam Scott fired an eight-under par 63 on Saturday to match Masters champion Charl Schwartzel of South Africa and American Bubba Watson for the lead after the second round of the Deutsche Bank Championship.
The three stars, all of whom began off the 10th tee, topped the leaderboard at 10-under par 132 after 36 holes at the $8 million event, the second leg of the season-ending playoffs US PGA playoffs that offer a $10 million top prize.
Schwartzel birdied six of seven holes after making the turn for a 66 while Watson, seeking his third title of the year, carded a 64 - but it was Masters runner-up Scott's bogey-free round that was the day's lowest.
"This was a really solid round," Scott said. "I turned it around with the putter after a balky day on the greens yesterday. I'm happy to be back in the mix again."
Scott, who won last month's World Golf Championships event at Akron, had six birdies and an eagle at the TPC of Boston layout.
A 25-foot birdie putt at the ninth to grab the lead alone was inches off, but Scott, the 2003 Deutsche Bank winner, still considered it among his best rounds of the year.
"This one is right up there," Scott said. "Hopefully the weather holds up and we have another good one tomorrow."
Schwartzel took a bogey at the par-3 11th and after a birdie at the par-3 16th stumbled again with a bogey at the par-5 18th.
He then birdied four holes in a row starting at the first, with back-to-back birdies at the par-4 sixth and par-5 seventh completing his run to the top.
Watson, who won earlier this year at Los Angeles and New Orleans, fired six birdies, a bogey and an eagle on the par-5 seventh hole for the second day in a row.
"All we were trying to do was hit the front edge," Watson said of the eagle. "The pin was in the front. I hit 5-iron to about 12 feet and then somehow made that putt."
Putting has been a frustration for Watson for much of the year.
"I've been uptight for the last few months. I haven't had fun. Hopefully this week changes it," Watson said. "I've just been really angry on the course. I couldn't make any putts. This week I made a few putts and here I am."
American Brandt Snedeker, aided by a hole-in-one at the 146-yard 16th, also fired a 64 to move within a stroke of the lead with American Nick Watney another shot adrift.
South African Ernie Els and Americans Rickie Fowler, Chez Reavie, Jerry Kelly and Jason Dufner were next on 135.
Snedeker's ace came from a 9-iron with the wind taking the ball left. It hit right of the cup and spun into the hole.
"It was just kind of one of those fluke things where I hit a great shot at the right time," Snedeker said.
Australian Greg Chalmers also aced the 16th in a round of 65 that left him on 137.
Els, who was 99th among 100 players to qualify for the event, fired a bogey-free 65. The three-time major winner began on the back nine and birdied four of his last six holes to join the contenders.
Els is trying to reach the top 70 in season points to qualify for the next playoff event in two weeks at Chicago, with an ultimate goal of cracking the top 30 to reach the Tour Championship in three weeks at Atlanta.
"When you’ve made Atlanta, you’ve had a good year, so I’m trying to get to that week," Els said.
"If you don’t really play well, you don’t advance. That’s probably what I needed to get my game back in shape. I’ve really worked hard on all aspects of my game. I feel like things are really starting to fall into place now."
Els is using a belly putter and his putts have started to fall more often since the switch.
"I've been working quite hard to get some kind of game going, and it seems like I've got it going a bit now," Els said. "The putter is starting to cooperate a little bit better."
Spain's Sergio Garcia fired a 65, his lowest US PGA round since the Players Championship in May, to stand on 136. Garcia's last tour triumph was at the 2008 Players.
"I probably deserved to win already by now, but at the same time, it has been a process," Garcia said. "My game has been getting better. That’s why I look at it very positively."
Scores on Saturday after the second round of the $8 million US PGA Deutsche Bank Championship (par-71, USA unless noted):
132 - Bubba Watson 68-64, Charl Schwartzel (RSA) 66-66, Adam Scott (AUS) 69-63
133 - Brandt Snedeker 69-64
134 - Nick Watney 67-67
135 - Rickie Fowler 68-67, Ernie Els (RSA) 70-65, Jerry Kelly 66-69, Jason Dufner 68-67, Chez Reavie 67-68
136 - Sergio Garcia (ESP) 71-65, Brendan Steele 69-67, Ryan Moore 68-68, Luke Donald (GBR) 66-70, Jason Day (AUS) 67-69, Brian Davis (GBR) 70-66, Troy Matteson 65-71
137 - Zach Johnson 68-69, Chris Kirk 71-66, Yang Yong-Eun (KOR) 66-71, Webb Simpson 69-68, Blake Adams 70-67, Greg Chalmers (AUS) 72-65, Scott Stallings 72-65
139 - Geoff Ogilvy (AUS) 69-70, Andres Romero (ARG) 71-68, John Senden (AUS) 70-69, Carl Pettersson (SWE) 69-70, Graeme McDowell (NIR) 71-68
140 - Justin Rose (GBR) 70-70, Fredrik Jacobson (SWE) 74-66
141 - Aaron Baddeley (AUS) 72-69, Robert Karlsson (SWE) 74-67
142 - Rory Sabbatini (RSA) 67-75, Ryuji Imada (JPN) 73-69, Padraig Harrington (IRL) 69-73, Robert Allenby (AUS) 70-72
143 - Jhonattan Vegas (VEN) 71-72, Martin Laird (GBR) 71-72, Phil Mickelson 70-73, Marc Leishman (AUS) 71-72, Camilo Villegas (COL) 73-70
Failed to qualify:
144 - Ian Poulter (GBR) 72-72
145 - Brendon de Jonge (ZIM) 68-77, KJ Choi (KOR) 70-75, Vijay Singh (FIJ) 75-70
147 - Charlie Wi (KOR) 73-74
WD - Trevor Immelman (RSA) 78