Canadian Nick Taylor fired a six-under par 66 to take a two-shot lead after the second round at the AT&T Pebble Beach Pro-Am.
Taylor birdied four of his last five holes to take his first 36-hole lead on the PGA Tour, at 14-under.
Australia’s Jason Day is well-placed in second, after a superb 64 took him to 12-under overall.
Day holed a 40-yard wedge for an eagle on the par-five 14th.
Meanwhile Séamus Power is the pick of the Irish, after his second round of 68 - at Spyglass Hill - moved him to four under par for the championship.
Pádraig Harrington is level par following his 73 at Pebble Beach while Graeme McDowell - a winner on the European Tour last week - has slipped well off the pace. He struggled to a 75 at Monterrey Peninsula on Friday and is adrift on two over par.
Defending champion Phil Mickelson moved up to third after going around in seven-under, leaving him on 11-under after two days.
Collated second round scores in the USPGA Tour AT&T Pebble Beach Pro-Am (USA unless stated, par 71):
Monterey Peninsula Country Club
132 Phil Mickelson 68 64
134 Dustin Johnson 69 65
135 Brandon Wu 69 66, Patrick Cantlay 66 69, Lanto Griffin 67 68, Kevin Chappell 68 67
136 Max Homa 67 69, Paul Casey (Eng) 71 65, Kevin Streelman 69 67
138 Kurt Kitayama 69 69, Sean O’Hair 73 65, Viktor Hovland (Nor) 70 68, Chesson Hadley 71 67, Zac Blair 69 69
139 Daniel Berger 70 69, Wyndham Clark 68 71, Charley Hoffman 67 72, Troy Merritt 69 70, Russell Knox (Sco) 74 65
140 Doc Redman 73 67, Ben Taylor (Eng) 73 67, Brian Gay 72 68, Adam Long 74 66, Brandt Snedeker 73 67, Kevin Kisner 72 68
141 Jimmy Walker 73 68, Smylie Kaufman 75 66, Jordan Spieth 70 71
142 Sebastian Cappelen (Den) 72 70, Steve Stricker 74 68, Kevin Na 75 67, Arjun Atwal (Ind) 75 67, John Senden (Aus) 71 71, Ryan Brehm 73 69
143 Peter Uihlein 73 70, Jason Dufner 73 70, Branden Grace (Rsa) 73 70, Adam Hadwin (Can) 74 69, Luke Donald (Eng) 72 71, Michael Gligic (Can) 72 71
144 Jim Furyk 74 70, Patrick Rodgers 76 68
145 Graeme McDowell (NIrl) 70 75
146 Pat Perez 71 75, Chris Stroud 76 70, Chad Campbell 74 72, Nate Lashley 73 73
147 D.A. Points 77 70
148 David Hearn (Can) 75 73, Martin Trainer 73 75, Si Woo Kim (Kor) 77 71
149 Austin Cook 78 71
Spyglass Hill GC
136 Matt Every 70 66
139 Nick Watney 73 66, Peter Malnati 70 69, Matthew NeSmith 68 71, Tim Wilkinson (Nzl) 69 70
140 Ben Martin 72 68, Seamus Power (Irl) 72 68
141 Matt Jones (Aus) 68 73, Brandon Hagy 73 68, Stewart Cink 69 72, Matt Kuchar 70 71, Tyler McCumber 71 70, Robert Streb 67 74, Matthew Fitzpatrick (Eng) 71 70
142 Chase Seiffert 66 76, Wes Roach 69 73, Henrik Norlander (Swe) 69 73, Alex Cejka (Ger) 69 73
143 J.B. Holmes 71 72, Harold Varner III 67 76, Vaughn Taylor 72 71, Nelson Lauta Ledesma (Arg) 73 70
144 Maverick McNealy 72 72, Chris Kirk 72 72, Vincent Whaley 71 73, Ryan Armour 70 74, Anirban Lahiri (Ind) 73 71
145 Xinjun Zhang (Chn) 71 74, Andrew Landry 76 69
146 Scott Stallings 73 73, Lucas Glover 70 76, Mark Hubbard 74 72, Zack Sucher 72 74, David Lingmerth (Swe) 72 74, Bol Hoag 71 75, Ted Potter, Jr. 72 74, Mackenzie Hughes (Can) 74 72, Tyler Duncan 73 73, Michael Gellerman 73 73
147 Kristoffer Ventura (Nor) 71 76, Michael Thompson 73 74, Dominic Bozzelli 76 71
148 Roberto Castro 74 74
149 Scott Brown 77 72, Bol Van Pelt 75 74
150 Brian Stuard 73 77, J.J. Henry 74 76
151 Hank Lebioda 74 77, Robert Garrigus 74 77
152 Kiradech Aphibarnrat (Tha) 73 79
153 Scott Ger Borba 75 78
Pebble Beach GC
129 Nick Taylor (Can) 63 66
131 Jason Day (Aus) 67 64
133 Charl Schwartzel (Rsa) 67 66, Christopher Baker 69 64
134 Scott Piercy 68 66
135 Harry Higgs 66 69
136 Alex Noren (Swe) 69 67, Keith Mitchell 69 67, Chez Reavie 67 69
137 Aaron Baddeley (Aus) 68 69, Justin Suh 67 70, Adam Schenk 68 69, Cameron Champ 71 66
138 Ricky Barnes 66 72, Richy Werenski 66 72
139 George McNeill 68 71, Jonathan Byrd 67 72, Fabian Gomez (Arg) 73 66
140 Beau Hossler 68 72, Scott Harrington 68 72, Greg Chalmers (Aus) 67 73, Kyung Ju Choi (Kor) 74 66, Doug Ghim 68 72, Jim Herman 67 73, Brice Garnett 70 70, Cameron Tringale 71 69
141 James Hahn 71 70, Joseph Bramlett 71 70
142 Rob Oppenheim 68 74, Aaron Wise 68 74, Josh Teater 70 72, Tom Hoge 69 73
143 Rhein Gibson (Aus) 74 69, Cameron Davis (Aus) 71 72, Mark Anderson 73 70, Padraig Harrington (Irl) 70 73
144 Joel Dahmen 71 73, Johnson Wagner 70 74, Rafael Cabrera-Bello (Spa) 70 74, Patrick Martin 73 71
146 Bill Haas 71 75, Rod Pampling (Aus) 73 73, D.J. Trahan 71 75
147 Kramer Hickok 74 73, Sung Kang (Kor) 74 73, Isaiah Salinda 74 73, J.J. Spaun 69 78
149 Satoshi Kodaira (Jpn) 76 73
151 Hunter Mahan 74 77
152 Tim Herron 78 74
153 Kevin Stadler 77 76
155 Sam Saunders 77 78
