Watch this key S&P 500 level next week: Trader

The S&P 500 closed down for the fourth straight week for its worst losing since 2011, but it doesn't yet resemble bear markets of years past, Stuart Frankel's Steve Grasso said.

Key was the 200-day moving average, he said, which is 1,906 in the S&P, which ended the day at 1,886.76, up 1.29 percent.

S&P 500 posts longest weekly loss streak since 2011

On CNBC's "Fast Money," Grasso said that past market performance hints at how long stocks.

Traders on the floor of the New York Stock Exchange.
Lucas Jackson | Reuters
Traders on the floor of the New York Stock Exchange.

"The last time we broke the 200-day, it was for a week," he said. "If we stay below it longer than Wednesday, I think it's a trend change."

Moody's downgrade of Russia was a potential headwind for stocks in the coming week, Brian Kelly of Brian Kelly Capital said.

"Normally, a downgrade of a sovereign country, nobody cares about, but given the fact that the currency has been under so much pressure, this could have a big impact next week," he said.

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Kelly pointed to the selloff in the IWM and high-yield bonds as reasons not to trust the one-day rally.

"But the largest point gains in Dow over time have come during bear markets," he added.

Still, Kelly said, economic issues facing Japan and Europe could provide more bad news for traders.

"So, for me, I don't see how you can trust this with all those negative catalysts out there," he said.

OptionMonster's Pete Najarian said the week's selloffs were all about technical and Ebola, but he also saw bright spots in quarterly earnings from the likes of Goldman Sachs.

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But that wasn't enough for Najarian to expect continued gains.

"I don't know that I trust this market," he said.

Triogem Asset Management's Tim Seymour sounded a more bullish tone.

"I think the market was oversold. I think oil was oversold," he said. "If we look at the trades that actually have worked for the last three days, I think you have a few more days there. I don't think you have to run out the door."