Judd Trump won the Masters title in January and has been one of this year's form players
Judd Trump, John Higgins and Mark Williams all suffered surprise defeats in the first round of the China Open.
Higgins lost six frames in a row in a 6-2 defeat against rookie pro Joe O'Connor, while world champion Williams lost 6-4 to 49-year-old Ken Doherty.
Masters champion Trump, who has also won two ranking titles this season, was edged out 6-5 by Robbie Williams.
Two-time champion Ding Junhui lost 6-3 to another 49-year-old, Thailand's James Wattana.
Wattana, a former world number three now ranked 119, won the last of his three ranking titles at the 1995 Thailand Open.
The former Asian number one had runs of 81, 99 and 98 against the current incumbent Ding, who has reached the quarter-finals of just one ranking event this season.
Trump trailed 3-0 to his opponent Williams, England's world number 64, who made a break of 119 in building that lead, but it went to a decider which lasted 65 minutes.
In that final frame, Trump trailed by 21 points when he played a loose safety on the green and his opponent secured the match.
Doherty had runs of 76, 62, 115 and 90 in his win over Welshman Williams - who himself made breaks of 91, 53, 75 and 71 - but the world champion heads into the defence of his Crucible title having not reached a ranking event semi-final since winning the World Open in August.
Scotland's Higgins, a four-time world champion, lamented: "Right now, I'm an also-ran for the World Championship,"
England's Barry Hawkins was also eliminated after a 6-5 defeat to Lu Ning of China.
Another Englishman, Kyren Wilson, eased to a 6-2 victory over Yuan Sijun while Peter Ebdon beat Yan Bingtao by the same score.
With the defeat of Mark Selby in the qualifying round and world number one Ronnie O'Sullivan's absence from the event, world number seven Neil Robertson is now the highest-ranked player left in the tournament.
