The turmoil in emerging markets that sent U.S. stocks tumbling last week may have set the stage for an even bigger U.S. stock decline.

"We came into the year thinking 2014 would be a much more challenging year for investors," Bruce Bittles, chief investment strategist at Robert W. Baird, told The Wall Street Journal.

Stocks are overvalued in relation to earnings and economic growth, he noted. Bittles anticipates a "stiff correction of 10 to 20 percent" sometime this year.

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The Standard & Poor's 500 Index has declined 3.4 percent so far this year.

In addition to weakness in emerging markets, experts point to the Federal Reserve's tapering of its bond-buying purchases as another negative for stocks.

And like Bittles, some are concerned about valuations.

At the end of 2013, the S&P Composite 1500 index, which covers about 90 percent of U.S. market capitalization, was priced at 18 times the earnings of its components, up 20 percent from a year earlier, Wayne Kaufman, chief market analyst at Rockwell Securities, told The Journal.

"We can't expect that to continue," he said.

To be sure, some experts think the market's correction so far this month will draw buyers. "This is the first major weakness in stocks we have seen for some time," James Paulsen, chief investment strategist at Wells Capital Management, told Bloomberg.

"We may be surprised how many buyers it brings into the stock market."

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