Ian Poulter failed to build on his first-round showing at the Deutsche Bank Championship after carding a 73 on the second day in Boston.
A 67 on Friday had Poulter in the mix but the poor form that has dogged him for much of 2014 returned on Saturday.
Ryan Palmer and Jason Day lead on eight under, with Poulter, who needs a captain's pick from Paul McGinley to make Europe's Ryder Cup team, six back.
World number one Rory McIlroy shot a 69 to move to three under at halfway.
McIlroy, who is hoping to finish top of the FedEx Cup standings, shot a 70 on the opening day.
Poulter is expected earn a wild card from Europe captain McGinley thanks to his previous success in the competition, but his form still appears fragile after two nightmare holes on Saturday.
A double-bogey at the first and triple-bogey at 16 saw Poulter tumble down the order.
Fellow Englishman Luke Donald - who also needs a wild card to make the Ryder Cup - was another to suffer a poor round, carding a 74 to fall to one over.