Augusta - Defending champion Jordan Spieth sank a 14-foot par putt at the 18th hole to keep a one-stroke lead over Rory McIlroy after Friday's second round of the Masters.
Both stars grinded their way around as ill winds gusted across Augusta National, the breezy conditions playing havoc with the world's most skilled shotmakers, who largely scrambled to contain the damage.
"I'm really happy with the round and how I grinded and battled out there," McIlroy said. "And I'm going to have to do that again tomorrow because it's going to be windy out there again."
Spieth struggled to a two-over 74, bogeys at the par-3 16th and 17th stripping a lead that had once been five shots to a single stroke with the 22-year-old American on four-under 140.
"It was a mental test. It was a battle," Spieth said. "Still leading. Can't complain about that."
Spieth is trying to join Tiger Woods, Jack Nicklaus and Nick Faldo as the only players to win the Masters two years in a row.
"It's almost a different tournament now," Spieth said. "Tomorrow is going to be more difficult given the same winds and crustier greens. I'll approach it as a difficult scoring day and try to stay patient."
Four-time major champion McIlroy, trying to complete a career Grand Slam by winning the green jacket, shot 71, with birdies at the par-5 13th and 15th and par-3 16th charging him to the top while rivals faded.
"It was very difficult," McIlroy said. "It was very hard to select a club. On the 12th tee, I felt a little lull in the wind. I just hit it straight away. That's the hardest thing out there, trusting clubs. It was tricky."
McIlroy is trying to become only the sixth golfer to complete a career Grand Slam by winning all four major titles at least once, joining Tiger Woods, Jack Nicklaus, Ben Hogan, Gary Player and Gene Sarazen.
It was the first Masters round since the third in 2007 without a round in the 60s.
But it resulted in world number two Spieth and third-ranked McIlroy -- who have combined to win four of the last six majors -- playing together in the last group in a showcase pairing sure to draw the largest crowd at Augusta National.
"Add a lot of excitement and buzz and atmosphere," McIlroy said. "But at the same time, I just need to focus on myself and make sure that I play another solid round of golf."US Amateur champion Bryson DeChambeau, a 22-year-old American who turns professional next week, nearly spoiled the star duo but a triple-bogey at 18 dropped him to level par overall.
"You don't want to finish with a triple but you can't worry about that," DeChambeau said. "I'm looking forward to the weekend."
Spieth would overtake Australia's Jason Day for world number one with a Masters win if the Aussie finishes outside the top five.
"It almost feels like a US Open where you have just got to survive," Day said of the blustery conditions. "I'm just trying to survive right now."
South Korean-born New Zealander Danny Lee and American Scott Piercy shared third on two-under 142.
Lee, trying to become the first Kiwi to win a US event since Michael Campbell took the 2005 US Open, fired 74, closing bogey-bogey to fall back.
"I'm just happy I'll get to play on the weekend and I'll have a chance," Lee said.
Piercy shot 72, unable to make a run after birdies on two of the first three holes.
"It's just blowing so hard, the wind is playing a huge part," Piercy said. "The greens are starting to dry out. If you get them downwind it's hard to stop the ball."
The only others under par after 36 holes were Japan's Hideki Matsuyama, Denmark's Soren Kjeldsen and American Brandt Snedeker on 143.
Masters 2nd round scores
140 - Jordan Spieth (USA) 66-74
141 - Rory McIlroy (NIR) 70-71
142 - Scott Piercy (USA) 70-72, Danny Lee (NZL) 68-74
143 - Hideki Matsuyama (JPN) 71-72, Soren Kjeldsen (DEN) 69-74, Brandt Snedeker (USA) 71-72
144 - Dustin Johnson (USA) 73-71, Bryson DeChambeau (USA) 72-72, Daniel Berger (USA) 73-71, Sergio Garca (ESP) 69-75, Kiradech Aphibarnrat (THA) 72-72, Danny Willett (ENG) 70-74, Shane Lowry (IRL) 68-76
145 - Chris Wood (ENG) 72-73, Bernd Wiesberger (AUT) 73-72, Jason Day (AUS) 72-73, Bernhard Langer (GER) 72-73, J.B. Holmes (USA) 72-73, Brooks Koepka (USA) 73-72, Troy Merritt (USA) 74-71, Smylie Kaufman (USA) 73-72
146 - Kevin Streelman (USA) 71-75, Kevin Na (USA) 72-74, Davis Love III (USA) 73-73, Jimmy Walker (USA) 71-75, Emiliano Grillo (ARG) 71-75, Angel Cabrera (ARG) 73-73, Lee Westwood (ENG) 71-75, Paul Casey (ENG) 69-77, Justin Rose (ENG) 69-77, Jamie Donaldson (WAL) 74-72
147 - Matthew Fitzpatrick (ENG) 71-76, Ian Poulter (ENG) 69-78, Cameron Smith (AUS) 74-73, Rafael Cabrera (ESP) 74-73, Romain Langasque (FRA) 74-73, Henrik Stenson (SWE) 72-75, Billy Horschel (USA) 70-77, Keegan Bradley (USA) 74-73, Harris English (USA) 74-73
148 - Charley Hoffman (USA) 71-77, Hunter Mahan (USA) 73-75, Matt Kuchar (USA) 75-73, Adam Scott (AUS) 76-72, Thongchai Jaidee (THA) 72-76
149 - Louis Oosthuizen (RSA) 72-77, Victor Dubuisson (FRA) 73-76, Martin Kaymer (GER) 74-75, Anirban Lahiri (IND) 76-73, Bill Haas (USA) 75-74, Kevin Kisner (USA) 77-72, Webb Simpson (USA) 77-72, Larry Mize (USA) 76-73, Justin Thomas (USA) 76-73, Patrick Reed (USA) 76-73
150 - Bubba Watson (USA) 75-75
151 - Phil Mickelson (USA) 72-79, Vaughn Taylor (USA) 74-77, An Byeong-Hun (KOR) 77-74, Trevor Immelman (RSA) 77-74, Marc Leishman (AUS) 74-77
152 - Branden Grace (RSA) 75-77, Charl Schwartzel (RSA) 76-76, David Lingmerth (SWE) 79-73, Tom Watson (USA) 74-78, Zach Johnson (USA) 72-80, Russell Knox (SCO) 79-73
153 - Graeme McDowell (NIR) 72-81, Jason Dufner (USA) 76-77, Chris Kirk (USA) 76-77, Rickie Fowler (USA) 80-73, Jim Herman (USA) 75-78, Derek Bard (USA) 76-77, Ernie Els (RSA) 80-73, Vijay Singh (FIJ) 80-73
154 - Mike Weir (CAN) 76-78
155 - Ryan Moore (USA) 80-75
156 - Sammy Schmitz (USA) 81-75, Robert Streb (USA) 81-75
157 - Mark O'Meara (USA) 77-80, Jin Cheng (CHN) 79-78, Fabin Gmez (ARG) 77-80, Andy Sullivan (ENG) 80-77, Sandy Lyle (SCO) 76-81
160 - Darren Clarke (NIR) 76-84
161 - Steven Bowditch (AUS) 79-82
163 - Ian Woosnam (WAL) 82-81
165 - Paul Chaplet (CRC) 83-82