Here's how long you should wait to buy again: Pro

After a three-day selloff for stocks, investors shouldn't expect a bounce just yet, Stuart Frankel's Steve Grasso said Monday.

The S&P 500 broke below its 200-day moving average, while the Nasdaq approached correction territory and the CBOE Volatility Index spiked 16 percent to 24.64, a closing level it hadn't seen since June 2012.

"This is all Ebola right now," Grasso said. "We've had growth concerns. We had Russia. We had Ukraine. We had the Mideast. We had everything. And today what kicked us off was more Ebola headlines when the market was trying to rally back."

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On CNBC's "Fast Money," Grasso said it would be prudent to wait, noting that the last time the S&P 500 broke below its 200-day moving average, in November 2012, it stayed there for "about a week or so."

"You need to close below this for a couple of days," he added.

Traders on the floor of the New York Stock Exchange.
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Traders on the floor of the New York Stock Exchange.

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RiskReversal.com's Dan Nathan said that the Federal Reserve's easy-money policy was to blame for the decline in stocks.

"The S&P is up 35 percent from the last time it closed below the 200-day moving average in November 2012," he said. "So, we have an economy here that is obviously doing better than the rest of the world, but we also know that the Fed has basically taken the training wheels off. So, we have a market for the first time in many years that doesn't have that implicit put from the Fed."

The S&P 500, Nathan added, was no longer the same safe-haven trade it used to be.

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"We cannot really decouple after we've been in a five-year recovery here, so I think it makes sense here," he said.

Nathan also wasn't a buyer—or a seller.

"I'm not telling you to go out and sell, but I'm just saying that we could be oversold on a near-term basis," he said. "And these have been great buying opportunities, but it may be different this time."

Private Advisor Group's Guy Adami said that the S&P would likely head toward a lower technical level.

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"Eighteen sixty-three is the level we bounced off of and through in May, the middle of May. I think that's where we trade down to," he said. "We've been flagging $103 in the IWM. That feels like it's in place, as well."

Lower crude oil prices "could be a tailwind," Karen Finerman of Metropolitan Capital Advisors said.

"Oil, I think, is a proxy for fears of an economic slowdown," she added, noting that the VIX "just went nuts today, closing today on the absolute highs."

The downward trajectory for stocks could continue, Finerman said.

"When things are trading down in integers, which we saw all over the place today in so many different industries, that tells you something else beside rational thought is going on," she said. "It could go on a lot longer."