Graeme McDowell was left to rue a poor finish despite setting the clubhouse target in the first round of the WGC-HSBC Champions event in Shanghai.
McDowell played his first 12 holes in seven under par at Sheshan International but dropped two shots in the last six to card an opening 67 in the second event of the European Tour's Final Series.
Starting from the 10th, the Ryder Cup star birdied his opening hole and picked up further shots on the 13th, 14th, 16th and 17th to race to the turn in 31, before birdies at the second and third took him well clear of a star-studded field featuring 40 of the world's top 50.
However, the former US Open champion dropped his first shot of the day on the fourth and paid the price for missing his only fairway of the round on the 603-yard eighth hole, a par-five which had so far given up just two birdies.
Shane Lowry is the only other Irishman in action in China, but the Offaly man had a disappointing start, hitting six over in his opening round.
At five under par, McDowell enjoys a two-shot lead over Ryder Cup opponent Rickie Fowler and fellow Americans Chris Kirk and Brandt Snedeker.
American Dustin Johnson claimed the title 12 months ago with a winning total of 24 under par, but Justin Rose - who was fifth last year - had correctly predicted heavier rough and firmer greens would make scoring more difficult.
Rose, who was fourth in the BMW Masters on Sunday, was level par, while the winner at Lake Malaren - Germany's Marcel Siem - was also even for his round.
Spain's Miguel Angel Jimenez, who took 13 on the ninth hole during his final round last week, struggled to an opening 78, while FedEx Cup winner Billy Horschel managed just one birdie in a round of 80.