Rafael Nadal failed to reach his 100th ATP final after losing in three sets to unseeded Uruguayan Pablo Cuevas in the Rio Open semi-finals.
The 14-time Grand Slam champion and top seed won a first-set tiebreak and saved two set points in the second, but was beaten 6-7 (6) 7-6 (3) 6-4.
"I lost an opportunity," Nadal said. "I have to accept it and keep working to try to change the dynamic."
World number 45 Cuevas will meet the unseeded Guido Pella in the final.
The Argentine won 6-1 6-4 against Austrian fifth seed Dominic Thiem, who beat world number five Nadal in the last four of the Argentina Open last week.