Justin Rose opened with two bogeys in the first four holes and saw his lead shrink to three strokes early in Friday's second round of the 85th Masters while Augusta National allowed a charge by rivals.
The 40-year-old Englishman fired his lowest Masters round in 59 trips with a seven-under par 65 on Thursday to lead by four, matching the largest 18-hole Masters lead since 1941.
Rose, a two-time Masters runner-up, equalled the record of Jack Nicklaus by leading the event for the fourth time after 18 holes.
Reigning Olympic champion Rose, whose only major title came at the 2013 US Open, made an early start Friday in cool and overcast conditions while most of his nearest rivals were among the afternoon starters.
After landing in trees to the right off the first tee Friday, Rose pitched back into the fairway and limited his damage to a bogey five.
At the 575-yard par-5 second, Rose found the fairway with a 3-wood, then was short of the left side of the green before chipping his third within three feet of the cup and rolling in the birdie putt.
Rose parred the fourth, then came up shy of the green at the par-3 fourth. His putt up a rise barely clung to the edge of the green and from there he putted to three feet and dropped a putt in the right side for bogey.
That left Rose on 6-under and three atop two early chargers.
Australia's Marc Leishman opened with three straight birdies to share second on 3-under overall while Austrian Bernd Wiesberger opened with four birdies in the first five holes and added another at the par-5 eighth to join the pack at 3-under.
Only 12 players finished under par in the first round, with Japan's Hideki Matsuyama and American Brian Harman sharing second on 69, both teeing off in the final five afternoon groups.
In the first round, Rose had bogeys at the first and seventh holes, then took apart a firm and fast Augusta National layout that humbled a world-class field.
His deft iron play and deadly accurate putting in a 10-hole run of an eagle and seven birdies from the eighth to 17th hole showed slow starts would not deter him.
"I putted the ball beautifully and read the greens unbelievably well," Rose said. "If you had said to me walking up the eighth hole, I'd have said no chance, this course is playing a little too tricky for that.
"But it's incredible. It's a good reminder that you just never know what can happen out there, just to stick with it on the golf course."
At 2-under were South African Christiaan Bezuidenhout and an American trio -- Masters debutante Will Zalatoris, 2012 US Open champion Webb Simpson and 2018 Masters winner Patrick Reed.
Three-time major winner Jordan Spieth, who snapped a four-year win drought last week in Texas, was on 71 despite a triple bogey at the ninth.
World number three Jon Rahm, who only arrived at Augusta National on the eve of the event, was on 72. The Spaniard was with his wife Kelley, who gave birth to son Kepa on Saturday.
- Johnson, Koepka on 74 -
Top-ranked defending champion Dustin Johnson opened on 74, as did Brooks Koepka, a four-time major winner coming off right knee surgery last month.
Second-ranked Justin Thomas, who can overtake Johnson for world number one with a victory this week, was on 73, as was another American, 2020 PGA Championship winner Collin Morikawa.
Reigning US Open champion Bryson DeChambeau opened on 76, his long-driving game thwarted by Augusta National. DeChambeau drove over the green to double-bogey the par-3 fourth.
Four-time major winner Rory McIlroy struggled to his worst opening round at the Masters with a 76 on a day that saw him strike his father, Gerry, with a wayward second shot at the par-4 seventh.
England's 47-year-old Lee Westwood, runner-up at Bay Hill and the Players last month, shot 78 as he made a stumbling start to his bid to become the oldest Masters champion.