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Apple just sent up another red flag for stocks

Apple's break beneath a key technical and psychological level could signal more selling ahead for the stock — and for the broader market.

Asbury Research's chief market strategist, John Kosar, said Apple's close below the $92 level could mean there's roughly another $8 that could come off the share price. That could impact the S&P 500 and the Nasdaq 100, both highly correlated to the tech giant.

"Little levels get little reactions, and big levels get big reactions," he said. "You break a level like $92 that everybody can see ... more reaction in the marketplace. More people are aware of it and are acting on it."

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Apple closed Thursday at $90.32, down 2.4 percent. The $92 level is the Aug. 24, 2015, low. Kosar said the shares tested that level again when the stock market troughed on Feb. 11.

"If it closes below here, it's bearish. It's going to go lower ... when you break a support level, it usually begets more selling," he said. Kosar said the next downside level to watch is $84.77, which is the March 2009 uptrend, then watch $82.19, its December 2013 benchmark high.

"Apple is sending a negative signal, and you're getting more people to articulate it's a company that's one bad product away from a disaster," said Art Cashin, UBS director of floor operations at the NYSE.

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Scott Redler, partner at T3Live.com, said he shorted Apple when it hit $92, and he said it could go into the $70s based on one chart pattern.

"This stock has been technically weak for months and reinforced its technical damage with a gap down after earnings that was never filled. Now a hard break below this $92 area triggers a head and shoulders top pattern that gives a measured move for the stock to the $70s with first intermediate support at $86-ish. Closing below and staying below $92 keeps traders thinking bearish," Redler said in an email.

Thursday's sell-off came amid concerns about iPhone sales and the upcoming iPhone 7. Stocks turned lower Thursday morning as Apple sold off. The Nasdaq was the first of the major indexes to turn negative.

"It's statistically correlated to those indexes," said Kosar of the Nasdaq 100 and S&P. "If Apple drops another 6 to 9 percent, the correlation is likely to have an adverse affect on the broader market."

Read MoreApple hits near 2-year low

Cashin said what ails Apple has spread across technology shares. "None of the techs are doing well. There's a whole rethink of the technology area," he said. "People are beginning to say maybe that's not the growth area we think it is."

Peter Boockvar, chief market analyst at The Lindsey Group, said Apple is one of the top two stocks in the S&P and Nasdaq. "You have to look at it from that perspective," he said. "I've always said it's its own asset class."

"The issue with Apple is it's spilling over into the Apple suppliers, and it very well may be the case that Apple is the greatest technology company since sliced bread," said Boockvar. "If Apple gets such a low mulitple, why should I pay a higher price for grade B companies?"

Boockvar said Apple is over-owned. "A lot of people love Apple," he said. Even after the stock declines, "there's still this love affair with the company."

Apple was trading with a trailing price-earnings ratio of 10. The stock is down 14 percent year to date, and is 32 percent off its 52-week high of $132.97.

Apple was trading around $90.45 midafternoon Thursday. It had broken the $92 level earlier in the week but did not close below it. During Apple's decline, Alphabet surpassed it as the market cap leader Thursday. They are now both close to $494.7 billion.