Canadian Graham DeLaet, the third overnight leader, slipped from the top of the BMW Championship leaderboard into a tie for seventh with Seung-Yul Noh, Friday.
The Weyburn, Saskatchewan native had a 2-under 70 and is tied for seventh at minus-10 with Noh, who shot a 6-under 66 on Friday.
Vijay Singh fired a 6-under 66 on Friday to jump into the lead at the midway point of the BMW Championship, the third PGA Tour Playoff event.
Singh finished 36 holes at 13-under 131 and is one shot clear of some major stars at Crooked Stick.
Rory McIlroy, the No. 1 player in the world, a first-round co-leader, last week's Deutsche Bank Championship winner, the FedExCup points leader and the PGA champion, birdied the last for a 4-under 68.
"It wasn't as good a day as yesterday," said McIlroy. "I didn't hit the ball quite as well, but scored well and did enough to go out there and shoot another good number and set myself up in a good position going into the weekend."
Tiger Woods played in the same group with McIlroy the first two rounds and also birdied the 18th for a 5-under 67. He matched McIlroy and Ryan Moore, who carded a 66 on Friday, at 12-under 132.
"Today was a struggle," admitted Woods. "I fought hard to shoot a number today, and the way I was hitting it, I figured if I could get to double digits under par it would be a good accomplishment. I got a couple more out of it."
Lee Westwood had a 7-under 65 and is tied for fifth with Bo Van Pelt, the second first-round co-leader, who had a 3-under 69 in round two. That pair is knotted at 11-under par.
The top 30 on the FedExCup points list advance to the Tour Championship in two weeks.
Friday's leader could use a big week since he's 49th.
Singh won the FedExCup in 2008 and that was the last year he won on tour.
With tee times moved up to avoid bad weather in the afternoon, Singh teed off on No. 10 Friday morning. He missed his second at the par-5 11th hole left, but chipped to eight feet and poured in the birdie putt.
Four holes later, at the next par-5, the 15th, Singh knocked his second to 12 feet. He missed the eagle try, but tapped in for birdie. The 3-time major champion got to 10-under par thanks to a 4-foot birdie at the 18th.
That started a great run for Singh. He holed a pair of 3-footers for birdie at one and two, then drained a 15-footer for his fourth straight birdie.
"That kind of got me going," Singh said of his birdie streak.
Singh may have thought those birdies got him "going," but the fourth was a hiccup. He missed his approach left, pitched to 12 feet and couldn't convert his par putt.
Singh was back down to 12-under par and consecutive pars kept him at that number. At the ninth, Singh hit another beautiful second on a par-5, once again to 12 feet. He narrowly missed the eagle putt, but made birdie and took the second-round lead.
"I've got to keep it going," said Singh. "I've been playing well for two days for a while now, but I need four days of good playing. Sooner or later I think four days is going to happen, and hopefully it starts this week."
Singh has had some trouble putting four rounds together.
After top 10s at the Open Championship and Canadian Open, Singh was a second- round co-leader at the PGA Championship. He played in the last pairing Saturday with Woods, but went 74-77 and tied for 36th.
He's made the cut in both Playoff events and had a 68-69 last week at the Deutsche Bank Championship, but even this Hall of Famer is mystified about his inability to finish.
"I have no idea," admitted Singh. "I don't know, just I guess I want it so bad that I get in my own way, so I just have to get out of my own way and just play. Last weekend I played better but I didn't play well the first two days."
Reigning FedExCup champion Bill Haas fired an 8-under 64 in round two and moved into a share of ninth with Graeme McDowell (67), Dustin Johnson (67) and Padraig Harrington (65). The group finished at 9-under 135.
Thursday's final leader, U.S. Open champion Webb Simpson, struggled to a 3- over 75 and fell into a tie for 33rd at minus-5.
NOTES: Phil Mickelson shot a 5-under 67 and is tied for 13th at 8-under par...Defending champion Justin Rose managed a 2-under 70 and shares 22nd at minus-7...There is no cut in this event.