Apple's October earnings report could be a big factor in determining whether or not U.S. stocks get a fourth-quarter rally.
"The fact that Apple can't get going is negative for the market," said Marc Chaikin, CEO of Chaikin Analytics. The stock closed out the third quarter with a whimper.
As the overall market gained on the last day of the quarter, Apple underperformed Wednesday, closing up about 0.8 percent while the S&P rallied 1.9 percent. Apple fell 0.65 percent Thursday, while the S&P squeezed out a 0.2 percent gain.
"The size and volatility in this (is similar to) small cap issues, which speaks to uncertainty," said Howard Silverblatt of S&P Dow Jones Indices. "Apple's volatility is so high and the market is so emotional right now. Earnings season will make a big difference here."
Apple's fiscal fourth quarter results are scheduled for release after the bell on Oct. 27. Investors will scour the report for news on iPhone sales, especially in China.
"If those (quarterly) numbers don't come through, this correction will continue into a bear market," Silverblatt said. "The earnings are that important. Apple has good numbers but the market always expects more."
Here's what investors are closely monitoring: