Seventh seed Juan Carlos Ferrero made a surprise first-round exit from the World Indoor Tournament in Rotterdam on Monday after a 7-5, 6-1 defeat by Russian qualifier Teimuraz Gabashvili.
The Spanish former world number one, now ranked 20th, was humbled in a 75-minute match by the world number 132.
"I didn't play my best tennis from the beginning and felt slow today after I had some stomach problems yesterday," Ferrero told reporters.
"I played some good points today but overall I made too many mistakes."
The 2003 French Open champion had made a good start to this year, reaching the fourth round at last month's Australian Open and making the final of the Auckland Open.
Monday's defeat followed a second-round exit from the Marseille Open last week.
"My goals for this season are just getting back in the top 10 and till this match I have played well," he said.
Earlier on Monday, Germany's Michael Berrer reached the second round following a 6-3, 6-2 victory over compatriot Matthias Bachinger.
