Dominic Thiem was forced to delay his comeback as he withdrew from the Cordoba Open due to injury.
The former world number three has not played on the ATP Tour since damaging his wrist in Mallorca last June but was due to face Tomas Martin Etcheverry or Nicolas Jarry in Argentina.
However, the 2020 US Open champion confirmed on Monday: “In the last days, I suffered a minor injury between my knuckles, a little strain of my ligament.
“The positive thing is the wrist is perfectly fine, but I’m suffering pain in my hand and also lacking practice, so I have to pull out.
“I’m very sad, but I’m going to come back once I’m 100 per cent fit, and thank you so much for the great and warm welcome I had here in Cordoba.”
Thiem’s withdrawal makes for a potentially simpler quarter-final draw for Pedro Martinez, who came through a marathon contest on Monday against Thiago Monteiro.
The eighth seed, who will next face Juan Ignacio Londero, won 4-6 6-4 7-6 (7-4) in a match lasting just under three hours.
There was an even longer battle between Juan Pablo Varillas and home favourite Facundo Bagnis, who was defeated 6-4 5-7 7-6 (7-5) after three hours and 17 minutes on court. Varillas will play Albert Ramos-Vinolas or Andrej Martin in the next round.
Jaume Munar also sealed his progress, defeating Benoit Paire in straight sets.