Spain's Rafael Nadal lost in the semi-final of the Argentina Open, going down 4-6 6-4 6-7 to Austrian Dominic Thiem.
Nadal, the world number five and defending champion, failed to convert a match point at 5-4 in the final set.
The nine-time French Open winner is top seed for a tournament in Rio de Janiero next week that also includes British number two Aljaz Bedene.
Thiem, 22, will be looking for his first ATP singles title of the season in Sunday's final.