"It's complicated because the time between one match and another is very short," said Lugano, who limped off after damaging a right knee ligament during Uruguay's quarter-final win over Ghana.
Lugano's absence would be another blow to "La Celeste", who will also miss striker Luis Suarez in Tuesday's match in Cape Town. He is serving a one-match ban for handling the ball on the line against Ghana in the last moments of extra time.
"I was lucky enough to train and run in a straight line without pain, which is good news because it's only 48 hours since I was injured," he said.
"Now we'll have to wait until the last minute. The pain is not what matters, the point is to be 100 percent ready for a match of this level and be honest with my teammates and country. Tomorrow I will evaluate if I'm OK or not."
