Torres missed Liverpool's draw with Fulham last weekend as a result of the problem and was due to return to Spain to see a specialist for a second time this week.
But the volcanic ash cloud that has been causing travel chaos across Europe delayed Torres' trip and Benitez, whose side host West Ham on Monday, is nervously awaiting news.
It has been reported that Liverpool fear Torres will need more surgery after going under the knife in January and that his season, and possibly his participation at the 2010 FIFA World Cup™, could be over.
Asked if Torres will feature again in the current campaign, Benitez told the News of the World: "I don't know. He feels good and says the knee is fine, but we need the opinion of the specialist. He was supposed to see the specialist on Friday, but because of the cancelled flights there was a problem."