Buenos Aires: Carlos Alcaraz admitted to being "far from my true level" in a defeat to Nicolas Jarry at the semi-finals of the ATP Buenos Aires tournament on Saturday.
The defending champion's surprise straight-sets loss to the Chilean came in the Spaniard's first tournament since he lost in the quarter-finals of the Australian Open.
Two-time Grand Slam champion Alcaraz had been hoping to reach his first final since falling to Novak Djokovic at the Cincinnati Masters in August, and to clinch a first title since Wimbledon last July.
"It's a difficult defeat for me," Alcaraz said after the 7-6 (7/2), 6-3 loss.
"It really hurts. There are lots of things to improve. I played good tennis but I am far from my true level."
Alcaraz broke Jarry's service in the second set on the clay in Buenos Aires but immediately lost that advantage and found there was no way back after Jarry claimed the decisive break in the eighth game.
"It was a complicated tournament, the first on clay for a long time," Alcaraz said. "I didn't take the opportunities I had, I didn't play the tie-break well and it shows."
Jarry, the world number 21, will face Argentine wildcard Facundo Diaz Acosta, ranked 87, in Sunday's final.