Tiger Woods and Rory McIlroy slipped off the pace after round two of the BMW Championship in Philadelphia.
Ryder Cup rivals Woods and McIlroy held the overnight advantage after opening rounds of 62, but the American finished the day five shots off the lead as successive bogeys on the closing holes - including three putts at the last - proved costly.
McIlroy is four adrift after American Xander Schauffele took the lead on 13 under par at Aronimink Country Club, Newtown Square.
Briton Justin Rose is two behind in second after a flawless second round of 63 on Friday and there is a four-way tie for third between Americans Keegan Bradley and Rickie Fowler, Sweden's Alex Noren and Hideki Matsuyama of Japan.
McIlroy's 69 saw him fall six places to equal seventh on nine under, while Woods is tied for 12th.
The 14-time major champion followed up his 62 on Thursday - his lowest round since 1999 - with three birdies and three bogeys for a level-par 70.
Woods, who was this week named as a wild card pick for the Ryder Cup, said on pgatour.com: "I hit it just as good and putt it just as good. Nothing went in. That's the way it goes.
"That round today was easily six, seven-under par. It turned into even par which is not what I needed to do today."
Overnight rain and thunderstorms forecast for Friday afternoon saw tee times brought forward.
And Schauffele followed up his opening 63 with a 64, featuring seven birdies and a bogey.
Schauffele narrowly missed out on an automatic spot in Jim Furyk's United States Ryder Cup team and could earn the fourth and final wild card pick with a strong performance this weekend.
He said: "I feel like I'm sort of on a mission here. I have lots to prove to myself...and I just want to win and just handle my business."