Five-time world champion Ronnie O'Sullivan was knocked out in the first round of the China Open despite making a maximum 147 break.
O'Sullivan, 42, made the 147 in the fifth frame against fellow Englishman Elliot Slessor, who won 6-2 in Beijing.
O'Sullivan has one chance remaining to become the first player to win six ranking titles in a season.
He has won the English Open, Shanghai Masters, UK Championship, World Grand Prix and Players Championship.
However, it was the second time this season, after the Northern Ireland Open, that world number 73 Slessor has defeated O'Sullivan, who looked largely out of sorts in an error-strewn performance.
O'Sullivan, on 33 ranking titles overall, is level with Stephen Hendry, Ding Junhui and Mark Selby in winning five major titles in one campaign.
Elsewhere, defending champion and world number one Selby made it through with a 6-4 win over Scott Donaldson, China's Ding beat Craig Steadman 6-4, but former world champion Shaun Murphy suffered a shock 6-0 defeat by Chris Wakelin.
The China Open is the last event before the season-ending World Championship in Sheffield starts on 21 April.