Hedge fund pioneer Julian Robertson believes the euro could easily go below parity with the U.S. dollar, and if Greece exits the euro, it could happen fairly quickly, he said Tuesday.
The billionaire, who has been short the euro, cited contagion possibilities as the potential cause for a swift decline.
"If Greece goes, Spain—which really has a serious problem with individual debt throughout the country—Spain could have problems and they could be tempted to leave, too. And then perhaps Italy. That would be serious," the founder of Tiger Management said in an interview with CNBC's "Closing Bell."
However, if Greece stays in the euro, parity could take "a long time."
He also doesn't think Greece alone is terribly important and doesn't think it will trigger another global financial crisis.
Greece faces a 1.5 billion euro ($1.7 billion) payment due to the International Monetary Fund at midnight CEST (6 p.m. ET) Tuesday. A euro zone official said in a Reuters report that there's "no way" the Eurogroup will release funds for Greece to meet the deadline.
Another Eurogroup meeting is scheduled for Wednesday, and a new Greek proposal is expected.
A default is also looming in Puerto Rico, where the governor has said it can't pay its $72 billion debt. The island's ongoing problems are what led Robertson to short Assured Guaranty. The bond insurer has been hit by the island's debt woes, and Robertson thinks there is still substantial downside to the name.
"I think there's enough probably there to put them out of business just like Puerto Rico."