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."
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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.
Japan's debt load has been going on for years, Giddis noted, and the country has been able to manage it so far.
He'd also pay attention to China, whose economy has come "roaring down."
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Meanwhile, domestic investors should focus on Chicago and Illinois, BTIG chief global strategist Dan Greenhaus told "Closing Bell."
Chicago has unfunded pension liabilities and a public school system that has a $1 billion deficit for the fiscal year 2016. In June, Moody's downgraded the city's credit rating to junk level "Ba1" from "Baa2."
"There's going to be over the next couple of years some trouble in the muni bond market," Greenhaus said. "There are pension and domestic issues on the municipal bond front."
—CNBC's Stephen Desalniers and Reem Nasr contributed to this report.
Correction: This story has been updated to correct Kevin Giddis' title.