Shortly after Apple slashed its revenue guidance for the first quarter, Goldman Sachs said the iPhone maker will likely have to bring down numbers for the full year. As those results drop further, so will the company's shares, the firm said.

"We see the potential for further downside to FY19 numbers depending on the trajectory of Chinese demand in early 2019," Goldman's Rod Hall said in a note to clients late Wednesday.

Apple sees first-quarter revenue of $84 billion vs. a previous guidance of a range of $89 billion and $93 billion. Analysts expected revenue of $91.3 billion for the period, according to the consensus estimate from FactSet. Apple blamed most of the revenue shortfall on a slowing economy in China in the second half.

Apple shares dropped 9 percent to about $142 in trading Thursday after ending the first day of 2019 at $157.92. Goldman's Hall slashed his 12-month forecast to $140 from $182. He also lowered his full-year 2019 revenue estimate by 6 percent to $253 billion and his full-year EPS estimate by 10 percent to $11.66.