Lang, the founder of ExplosiveOptions.net, author of "Know Your Options" and part of the Trifecta Stocks newsletter team at TheStreet.com, said that the charts of several major averages are signaling more pain ahead.
"Lang believes that it's too soon to start picking at this market," Cramer said on "Mad Money." "In fact, he says buying here would be like trying to catch a falling knife."
Lang began with the weekly chart of the S&P 500. The index has already erased its gains for 2018, but Lang said two key indicators are signaling that it could still go lower: the 50-week moving average and the moving average convergence-divergence line, or MACD, which helps technicians anticipate changes in a stock's path before they happen.
"The darned thing just made its first weekly close below the 50-week moving average ... since early 2016 and this is something that really spooks chart-watchers," Cramer said.
Worse, the MACD made a bearish crossover this month, telling Lang the S&P could still trade lower. And his theory was only confirmed when he looked at the S&P's monthly chart.
"[The] first thing that jumps out at us is that we really haven't come down that far from the highs. Lang points out that this will be the S&P's first down month since March," Cramer said. "How low can we go? Lang thinks that the S&P could potentially fall to 2,300. That would be down 14 percent from these levels [and] could take several months."
But between its weekly and monthly charts, Lang said several measures of buying and selling pressure indicated that the index was more overbought than oversold, meaning there could still be weakness ahead.
"Lang says the momentum here is weak and the volume has been rising, suggesting that there's more pain to come," Cramer noted.
The Russell 2000, which tracks small-cap stocks, is "clearly the worst of the major indices," the "Mad Money" host said. Like the others, it has traded below its 50-week moving average, and the Russell's MACD indicator hasn't recovered since it "rolled over" in September, Cramer said.
"Lang points out that the volume here has been rising with heavy selling, meaning big institutional money managers are dumping these small-cap stocks," he said. "Lang wouldn't be surprised if it heads all the way down to its 50-month moving average. That's down about 10 percent from here."
All in all, while the declines will stop eventually, Lang's analysis and the charts are telling Cramer that the stock market isn't there yet.
"Bottom line? The charts of the major indices, as interpreted by Bob Lang, suggest we're not out of the woods," Cramer said. "Lang thinks we could have a lot more downside. I think it's OK to pick here myself. I like that some real down-and-outers rallied today. I also think we're way too oversold to get hammered here, at least for now, but I respect Bob's opinion and you need to know that there has been substantial technical damage that's been done to this market, and after this respite, it might not be done going down."