US Open champions Marin Cilic and Serena Williams kicked off their China Open campaigns with straight sets victories against battling underdogs on Monday, but Rafa Nadal suffered defeat in a rare doubles outing on his return from injury.
Williams, who won her 18th grand slam singles title in New York earlier this month, started sluggishly and found herself 5 0 and 40-15 down to Spanish qualifier Silvia Soler Espinosa.
However, the world number one saved four set points in a brilliant fightback before taking the match 7-5 6-2 to set up a second-round clash with another qualifier, Bulgarian Tsvetana Pironkova.
Elsewhere, former world number one Ana Ivanovic, had a far easier day by swatting aside Swiss teenager Belinda Bencic 6-2 6-1 to advance to the second round of the women's draw.
Ivanovic currently holds the eighth and final spot on the WTA's Race to Singapore standings with four places still up for grabs for next month's season-ending event.
Nadal in doubles loss
Also returning after an absence, albeit a longer one, was 14-time grand slam singles champion Nadal, who had been sidelined for over three months with a wrist injury.
The world number two teamed up with compatriot Pablo Andujar in the men's doubles but they lost 5-7, 6-4, 10-4 to Czech Tomas Berdych and American John Isner in his first match since losing in the last-16 at Wimbledon.
The Spaniard is the second seed in the men's singles draw and will face Richard Gasquet of France in first round action on the Beijing blue courts later in the week.
Cilic was able to capitalise on his unheralded opponent's mistakes with Bai's forehand faltering as the match progressed, allowing the Croatian to secure a break in each set to advance to the second round.