In other words, the market and oil are almost trading in lockstep. And after 12 p.m. oil turned lower and the market tumbled. Then, late day as oil pared losses, so did the S&P 500.
Looking ahead to Thursday, Cashin added if oil drops below $80 in a meaningful way, the stock market could go from bad to worse. "What happens in the energy markets will be very important," Cashin added in an appearance on "Closing Bell."
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"Below $80, oil will raise concerns about real deflation," Cashin said. "Northern European countries are already beginning to see literal deflation." If WTI slips below $80, Cashin says pros will fear deflation is wider spread that previously believed.
And, taken a step further, Cashin says if deflation becomes a global phenomenon, traders will run for cover. "It's a worldwide threat and it seems to be coming home to roost."