Top seed David Ferrer of Spain was bundled out of the $524,000 China Open by Israel's Dudi Sela on Thursday, while big-serving American Andy Roddick swept past compatriot Brendan Evans to book a quarter-final place.
Ferrer, who enjoyed a round-one bye, appeared listless on a centre court flooded with bright sunshine and lost 6-3, 6-3.
He found the target on only 54 percent of his first serves and ended up surrendering the match with a raft of unforced errors.
The world number five, who rushed to China after Spain wrapped up their Davis Cup semi-final win against the United States in Madrid on Sunday, said fatigue had played a part.
"Maybe I was a little bit tired, I didn't sleep too well these two nights, but that's no excuse because he played better than me," a gloomy Ferrer told reporters.
World number 92 Sela, who flew from Tel Aviv after helping Israel to beat Peru for a place in the Davis Cup World Group on Sunday, faces a quarter-final against another Spaniard, sixth seed Tommy Robredo who cruised to a 6-2, 6-3 win over Czech Ivo Minar.
Roddick, a member of the losing Davis Cup team on Sunday, also made the final eight, shaking off jet-lag and a scratchy start to brush aside qualifier Evans in straight sets.
After conceding an early break, the former US Open champion quickly found his rhythm, clubbing 17 aces on the way to a 6-4, 6-3 victory over the 187th-ranked Evans.
"It's a little tough going from clay last weekend in Spain, dealing with jet-lag and what-not, so I'm just happy to be here for the first round," the 26-year-old said.
Roddick and Ferrer are among a clutch of players vying for one of the four remaining places in November's Tennis Masters Cup in Shanghai, which groups the year's eight best-performing players.
Spain's Rafael Nadal, Swiss Roger Federer, Novak Djokovic of Serbia and Briton Andy Murray are already assured of places.
World number eight Roddick faces a quarter-final against former world number one Juan Carlos Ferrero after the Spaniard eased past compatriot and fifth seed Fernando Verdasco 7-5, 6-4.
Germans Rainer Schuettler and Bjoern Phau will meet France's Richard Gasquet and Chile's Fernando Gonzalez respectively in the other quarter-finals.