The veteran investor says that's because even more debt has accumulated in the global economy since the financial crisis, especially in the U.S. While Rogers isn't saying that stocks are poised to enter bear territory now -- or making any claim to know when they will -- he says he's not surprised that U.S. equities resumed their selloff Thursday and he expects the rout to continue.

"When we have a bear market again, and we are going to have a bear market again, it will be the worst in our lifetime," Rogers, the chairman of Rogers Holdings Inc., said in a phone interview. "Debt is everywhere, and it's much, much higher now."

The plunge in equity markets resumed Thursday, as the S&P 500 Index sank 3.8 percent, taking its rout since a Jan. 26 record past 10 percent and meeting the accepted definition of a correction. The Dow Jones Industrial Average plunged more than 1,000 points, while the losses continued in early Asian trading Friday as the Nikkei 225 Stock Average dropped as much as 3.5 percent.