Stocks drifted in a narrow range Thursday afternoon, as investors digested a raft of  corporate earnings reports.

Amid the mixed trading session, two well-known billionaire investors revealed they have soured on the U.S. stock market. 

Monday on CNBC, David Tepper, who oversees nearly $20 billion at Appaloosa Management, said he was light on stocks, heavy on cash and did not see much upside in the markets. 

While not outright bearish, billionaire activist investor Carl Icahn said he remains very nervous about overvalued S&P companies and under-funded pensions. 

Sharing Tepper and Icahn's cautious tone is Joseph Amato, president and chief investment officer at Neuberger Berman, with $255 billion in assets under management.   

Appearing on CNBC's "Power Lunch" Monday, Amato said there are a number of "structural headwinds" to growth. 

"U.S. economic expectations being revised lower for 2016 and 2017," said Amato. "Europe and Japan also remain challenged, although China and broader emerging markets are rebounding."

Amato suggests investors keep a diverse portfolio across several different asset classes, including fixed income and equities. 

"Use these opportfunities of shifts in valuations to make tactical moves," said Amato. "Our portfolio managers are keeping more cash than they typically have done, and taking advantage of increasing volatility entering the marketplace." 

One area Amato is particularly bullish on is emerging markets. 

 "Given we have reduced U.S. stock market exposure, we see emerging markets outlook improving amidst weaker dollar, stronger commodity prices and short-term improvement in Chinese growth."