With Greece's debt crisis in the spotlight, market pros are keeping their eyes out for other potential problems looming in the horizon.
The cash-strapped country defaulted on its 1.5 billion euro ($1.7 billion) payment due to the International Monetary Fund Tuesday. Meanwhile, a default is also expected in Puerto Rico, where its governor has said it can't pay its $72 billion debt.
Beyond that, Portugal would be the next country to look to for stability in the euro zone, Kevin Giddis, head of fixed income at Raymond James said Tuesday.
"Right now you can't really say it's an issue because if you look at Portugal, Spain and Italy and their 10 years and the way they are trading, the market isn't concerned about their being a next shoe to drop," Giddis told CNBC's "Closing Bell."
Portugal has a debt to gross domestic product ration of 133 percent. Italy is at 140 percent and Japan has a ratio of 200 percent.