Rory McIlroy closed with two bogeys to take the shine off his opening round at the Deutsche Bank Championship in Boston as he carded a one-under 70 in his opening play-off event.
The world number one was in contention to be among the early leaders after moving to three under with back-to-back birdies on the third and fourth holes, having started on the 10th.
McIlroy hit one of the shots of the day at the 202-yard par-three third at TPC Boston before rolling in a birdie from five feet.
It was his second two of the day after another brilliant iron into the 166-yard 16th was followed by an eight-foot birdie putt to wipe out an earlier bogey on the 14th hole.
After rattling an eagle attempt passed the cup on the par-five 18th, McIlroy made the return birdie putt from six feet to go under par for the day.
McIlroy followed his birdie on the third by driving the 298-yard par-four fourth, but his eagle attempt failed to drop as he finished out for a birdie.
At that stage he looked well set to set the early clubhouse lead but missed par putts from less than eight feet at both the eighth and ninth to slip back into the pack.
England’s Luke Donald and American Colt Knost both carded four-under 67s to take a share of the clubhouse lead, with US PGA champion Justin Day a further shot back having started his round with three straight birdies.
Jordan Spieth’s patchy form continued as the two-time Major winner carded a four-over 75 following on from missing the cut at The Barclays.
An excellent start to his second round helped Bradley Dredge assume the halfway lead of the M2M Russian Open by a single stroke.
The Welshman, whose last victory on the European Tour came at the Omega European Masters in September 2006, carded his second consecutive 66 to sit on 10 under overall, just ahead of England's Lee Slattery.
Dredge, one off the lead overnight and starting on the back nine, began in splendid fashion with birdies at three of his first four holes before picking up a shot on the 18th for the second day in a row.
Another birdie followed on the third before he closed his round with six straight pars at Skolkovo Golf Club, and the 42-year-old admitted his short game was a particular positive on Friday.
“For me the highlight has been the putting, I’ve been putting really well,” Dredge said.
“If I can keep that going and improve my iron play a little bit then that will be good for the weekend.
“I’m delighted. Back-to-back 66s and no dropped shots. I’m very pleased with that.”
Slattery was one over for his round after 10 holes, with two bogeys and a birdie, but he then charged up the leaderboard by birdieing five of his last eight holes.
The 37-year-old, who admitted afterwards that he had been battling dizzy spells throughout his round, said: “It’s one of the most bizarre days I’ve had on a golf course but fortunately I was swinging it well and it didn’t affect my golf much.”
Australia's Daniel Gaunt is third on eight under overall, one shot ahead of England's Ben Evans, Spain's Pablo Martin Benavides and Argentina's Estanislao Goya.
Michael Hoey made four birdies in his closing seven holes to card a five-under 66 and he will go into the weekend on five under.
Headfort golfer Brian Casey also had a strong back nine, making a birdie on the 10th and three straight gains from the 13th as he carded a three-under 68 to move to two under.
Niall Kearney was a shot further back on one under after a level-par 71, while Damien McGrane made a bogey at his final hole – the ninth – in a round of 72 that saw him make the cut on the number of one over.
Peter Lawrie missed out by a shot after a bogey on the ninth, the Dubliner carding a one-over 72. Kevin Phelan's 75 included an eagle and two double bogeys as he carded a 75 to finish on four over.