Rafael Nadal of Spain crashed out of the Rio Open after losing 1-6, 6-2, 7-5 to Italian Fabio Fognini in the semi-finals.
Fognini will clash with David Ferrer, winning against Austrian Andreas Haider-Maurer in the other semi-final, for the title, Xinhua reported Saturday
Nadal, who failed to reach the final in all three tournaments he has taken part in this year, will play next week in Buenos Aires.
Fognini said he was "super happy" after ousting the the "best (player) on this surface".
"I don't have words to describe this moment. It's the best match I have won so far in my career."
Nadal's compatriot Ferrer secured his berth in Sunday's final by eliminating Haider-Maurer 7-5, 6-1.
Ferrer has won all seven previous encounters against Fognini.
In the women's category, top-seeded Sara Errani and sixth seed Anna Schmiedlova of Slovakia will vie for the top prize.
While Errani clean swept Sweden's Johanna Larsson 7-5, 6-3, Schmiedlova fought bravely for a three-set 6-3, 4-6 and 6-2 victory over second seed Irina-Camelia Begu from Romania.
