Rory McIlroy finished 24 shots behind winner Xander Schauffele at the WGC-HSBC Champions in Shanghai.
The Northern Irish golfer carded a two-over-par 74 in his final round to finish 10 over for the tournament.
McIlroy's 72 on the first day was the only time he managed even par and he finished tied for 54th in the final leaderboard.
Schauffele beat Tony Finau in a play-off to win the title, with defending champion Justin Rose third.
In a disappointing week for McIlroy, his hopes of reining in Francesco Molinari at the top of the Race to Dubai standings were not realised as the Italian finished three shots ahead of him.
Finau, one of the few stars for the United States team at the Ryder Cup, took a three-shot lead into the final day but Schauffele birdied the final two holes to force a play-off.
The 25-year-old went on to birdie the sudden-death par-five 18th to win the title.