Australian Jason Day continued his sizzling form to tie American Ryan Palmer for the lead after the second round of the Deutsche Bank Championship in Norton, Massachusetts.
Despite an unexpected bogey on his final hole, Day carded a three-under-par 68 in fluctuating afternoon winds while Palmer shot a 71 in the morning at the TPC Boston.
They finished level at eight-under 134, one stroke ahead of Americans Matt Kuchar (66) and Billy Horschel (66) on a tightly-bunched leaderboard.
World number one Rory McIlroy, slowed by a double-bogey at the par-four 14th where his approach shot bounded 30 yards over the green into a hazard, fired a 69 to trail the leaders by five shots.
Day, the world number seven whose quest this year to win a first major title was ruined by a thumb injury, maintained the red-hot form he displayed last week to tie for second in the first of the PGA Tour's four FedExCup playoff events.
Eighty players made the cut, which fell at three-over 145, and several Americans with hopes of earning a late Ryder Cup spot bowed out early, including Brendon Todd, Kevin Na and 2012 FedExCup champion Brandt Snedeker.
The top 70 players on the FedExCup points list after the Deutsche Bank Championship advance to next week's BMW Championship in Englewood, Colorado where the leading 30 will qualify for the September 11-14 Tour Championship finale in Atlanta.