But the big action will be around Yellen, and the oil market could also respond if her comments move the dollar. The dollar has been sinking on low expectations for a rate hike. For the week, the dollar index was down 1.3 percent and was at 94.50 late Friday. Treasurys could also respond, with the Fed-sensitive two-year at 0.74 percent late Friday and the 10-year at 1.57 percent.

"I wish we had a Fed speak [volatility index]. I'm telling you it just spiked through the roof. It's all over the map. I'm confused about what they're trying to do," said James Paulsen, chief investment strategist with Wells Capital Management. "We've got people talking out of every side of their mouth. The Fed VIX is at its highest ever."

Paulsen said the comments by two Fed officials in the past week were particularly confusing. San Francisco Fed President John Williams said in a letter that the Fed should consider raising its inflation target to 3 percent and allow interest rates to be lower for longer. New York Fed President William Dudley then said in a television interview that the market was too complacent and the Fed could raise rates as early as September. Then Williams spoke again, suggesting the Fed could move soon to hike rates.

"The bigger story might be does the bond market break out as opposed to stocks? I'm not so sure a more hawkish Fed is necessarily bad for the financial markets," said Paulsen.