Markets will be keeping a close eye on Yellen's speech due later on Thursday for any hints on the inflation outlook which could also tip stocks in one direction or another.
Since the Fed's meeting last week, commodities have tanked, with copper down more than 6 percent and oil down nearly 5 percent. China, meanwhile, has become an even bigger source of concern for markets, now that some worry the Fed might see more dire economic problems that could spread to the U.S. economy.
Other analysts compared current price action to similar trends seen in October 2011 and July 1998.
Chief investment officer and chief executive at Fasanara Capital, Francesco Filia, said there is a good chance stocks will revisit lows seen last month and a further 10 percent correction from there is possible.
"I believe there is a good chance that the S&P tests August lows and I believe a further 10 percent correction from there opens then up as a possibility, before central banks blink and the upward trend resumes," Filia told CNBC, comparing the current dips to moves seen in 2011 and 1998.
In both cases, the S&P retested lows first within a couple of months, before rebounding, he said. Founder and CEO of DeMark Analytics, Thomas DeMark agreed.
"Both 2011 and 1998 peaked exactly 17 trading days off their respective August 2011 and 1998 closing lows prior to declining to a an upcoming lower low. Current S&P 500 peaked last week after a 17 day rally off its August 24 low. So far the three periods are in alignment,"DeMark said.
"Bottom line is the August 24 low should be undercut," he added.