French Open champion Rafael Nadal lost at the Shanghai Rolex Masters after playing despite being diagnosed with appendicitis.
The second-ranked Spaniard was defeated 6-3, 7-6 (8-6) by countryman Feliciano Lopez, who will take on John Isner of the US in the third round.
Nadal was diagnosed with the condition on Sunday and is taking antibiotics in an attempt to avoid surgery, the men's ATP World Tour said on its website yesterday.
Nadal returned to the tour last week after a three-month lay-off because of a wrist injury.
He said today he may have his appendix taken out later when he returns home to Mallorca.
He is scheduled to play in the Barclays ATP World Tour Finals starting on Nov 9 in London.