"I spoke to David this morning and yesterday, and it is the 'game changer' make no mistake about it," Cramer said on "Squawk on the Street." "He's very, very concerned."
The coronavirus has "certainly ruined the environment" for stocks that had been the case before the outbreak, Tepper told Cramer on the red carpet for 9th Annual NFL Honors show, one day before the big game on Feb. 2.
"You have to be careful, because it may be a game changer. So you've just got to be cautious," Tepper said at the time. Besides his investing interests, Tepper owns the NFL's Carolina Panthers.
On Jan. 17, as the S&P 500 was still powering higher before the coronavirus outbreak was in the daily headlines, Tepper emailed "Squawk Box" co-host Joe Kernen, saying he loves "riding a horse that's running."
However, he told Kernen then, "At some point, the market will get to a level that I will slow down that horse and eventually get off." Tepper did not specify when that might be.
The stock market went on to hit new record highs in mid-February before investors started to get concerned about the widening outbreak, which originated in the Chinese city of Wuhan in Hubei province in December.
On Monday, the S&P 500 plunged more than 7% shortly after Wall Street's open, triggering the first of three circuit breaker thresholds. Trading was paused for 15 minutes. When trading resumed, the S&P 500 cut some of those losses.
The S&P 500, as of Friday's close, was off more than 12% from its all-time high on Feb. 19. The past several weeks have seen huge market swings.
On Monday, oil prices plunged after OPEC's production-cut deal failed and the 10-year Treasury yield made shocking new lows just above 0.3% in a global flight to the perceived safety of bonds.
The Federal Reserve's emergency, intermeeting 0.5% interest rate cut last week has done little to support stocks and bond yields. The Fed's regularly scheduled March policy meeting is next week.
Cramer said Monday that the coronavirus crisis is signalling the end of monetary policy's effectiveness. "This is just the need for fiscal policy," he stressed, calling again for the federal government to provide assistance directly to businesses.
"If this in the end of monetary policy, obviously, [Tepper] wants more leadership. We all want more leadership," Cramer said.
Tepper is well-known for a 2010 market call he made on CNBC that super-low rates by the Fed, coupled with the central bank's massive bond-buying, would make most investment choices go up. The Fed-driven stock market rally that ensued at the time became known as the "Tepper rally." The market rally continued the entire decade.