World no. 2 Luke Donald needs to finish in the top seven at Zurich Classic to move back above Rory McIlroy and take the top ranking.
In the opening round of the tournament that looked unlikely to happen after Donald fired a one-over-par 73 on Thursday which left him eight shots adrift of the leaders at the Louisiana venue.
However, the Englishman stormed back into contention in the second round, by firing a seven under par 65. The effort moved Donald to six under par, six shots off the lead, held by Jason Dufner.
Dufner capped a bogey-free round with an eagle on the par-five 18th to reach 12 under and establish a one shot lead over Russell Knox, John Rollins and Ken Duke.
A further shot back on 10 under were Greg Chalmers, who also fired a 64, Steve Stricker and Ernie Els.
Defending champion Bubba Watson had his second straight 71 to make the cut by a stroke in his first tournament since his Masters win, with Northern Ireland’s Graeme McDowell joining him on two under after a disappointing second round 73.
Brian Davis was alongside Donald on six under, while fellow Englishmen Greg Owen and Justin Rose were a further shot back.
Zurich Classic second round leaderboard:
-12: Jason Dufner (US)
-11: Russel Knox (Scotland), Ken Duke (US), John Rollins (US)
-10: Greg Chalmers (Australia), Ernie Els (South Africa), Steve Stricker (US)
-9: Camilo Villegas (Colombia), Cameron Tringale (US), Graham DeLaet(Canada)
Selected others: -8: Rickie Fowler (US), Daniel Chopra (Sweden), Rocco Mediate (US)
-7: Ben Curtis (US), Charles Howell III (US), Kris Blanks (US), Chris Stroud (US)
-6: Luke Donald (England), James Driscoll (US), Stuart Appleby (Australia)
-5: Greg Owen (England), Justin Rose (England), Brian Davis (England)
-3: David Duval (US), Webb Simpson (US), David Hearn (Canada)
-2 : Bubba Watson (US) , Graeme McDowell (Northern Ireland)