U.S. stocks were flirting with a critical threshold on Wednesday that, if broken, could portend another 10% drop for the S&P 500, according to one technical analyst.

The S&P 500 SPX finished Wednesday at 6,624.70, just a hair north of its 200-day moving average at 6,615.70, FactSet data showed. The Dow Jones Industrial Average DJIA wasn't so lucky; the blue-chip gauge finished below its 200-day moving average for the first time since June. The Nasdaq composite COMP also closed below its 200-day moving average, although the index also finished below the critical trendline on Friday.

That leaves U.S. stocks in a precarious position. According to Jonathan Krinsky, BTIG's managing director and chief market technician, this is the third time the S&P 500 has tested the 6,600 level going back to October. If stocks sink on Thursday, the S&P 500 could break through the critical support level.

"We have little confidence of it holding as support," Krinsky said in written commentary shared with MarketWatch.

This technical setup means there is now a decent probability that the S&P 500 will fall all the way back to 6,000, Krinsky said.

More pressure on stocks emerged after the closing bell on Wednesday. Crude-oil prices (CL.1) (BRN00) continued to climb following an Iranian attack on Qatar's Ras Laffan energy hub. The Qatari Ministry of Foreign Affairs said in a post on X that the attack resulted in fires causing significant damage to the facility. It also denounced it as a "dangerous escalation."

Also, shares of Micron Technology $(MU)$ were lower after hours, even after the company delivered a blowout earnings forecast and earnings beat. Krinsky had said earlier that the stock's reaction could have a big impact on the broader market, particularly the all-important semiconductor industry, on Thursday.