The "Mad Money" host said a colleague of his at RealMoney.com is warning that "we're really cruising for a bruising" beyond the 1.56% decline Tuesday by the index.
Bob Moreno, chartist at RightViewTrading.com who projected in February that the market had more room to run, warns of a possible plummet in the large-cap index.
"Now those same charts tell Moreno that we're approaching an important moment and he's predicting a major sell-off from these levels, a 10% decline in the S&P," Cramer said.
That would bring the S&P below 2,620 from its 2,893.06 Tuesday close.
Since its low following the major December sell-off, the S&P 500 has gained about 27%. The index made a series of higher highs and higher lows during that expansion, but Moreno is convinced that momentum was disrupted in September when it produced a lower high, Cramer explained perusing the weekly chart of the S&P 500.
According to FactSet, the S&P 500 posted a closing high of 3,025.86 in late July and failed to break past 3,010 in September, a potential peak. Moreno, Cramer said, determined that to be a "double top," which is a bearish technical reversal pattern.
"Moreno believes the S&P is going to test its floor of support again, only this time that floor is at 2,825," Cramer said. "But if it fails, and he thinks it will, another floor at 2,725. That's where the S&P bottomed in March and June."
"Unfortunately, he doesn't see that trading floor ... holding either," Cramer said. "If the S&P breaks down from the current consolidation pattern, we could have not a little but a lot more downside."
There are more bearish indicators in Moreno's analysis. He notes the Moving Average Convergence Divergence indicator had a bearish crossover, which means momentum is slowing, and the Chaikin Oscillator supply/demand indicator dropped below its center line, which means money flow is negative, Cramer said.
"He's hoping the S&P 500 can find a floor at the 2,600 level. ... That's still a long way from a retest of last December's lows, but it's pretty horrible," he said. If the floor at 2,600 fails, Moreno "did say when we talked to him that if this fails, we could revisit [the December] level."
Chartists analyze past price action in stocks to forecast future price direction.
"Do I agree? Moreno's views echo my own for vast swathes of the market, but as someone who likes individual stocks, I'm ready for chance to buy best-of-breed names at bargain basement prices," Cramer said.