Shares of Apple started the week in the red after a number of analysts trimmed their iPhone estimates based on firms' checks. And according to a highly regarded technician, the charts point to even more pain.

"The very fact that it's no longer in an uptrend is a problem," said Carter Worth of Cornerstone Macro on CNBC's "Fast Money," referring to the angle of Apple's chart.

According to Worth, after a long well-defined uptrend that dates back to 2013, Apple shares have now been under pressure for quite some time. "Clearly there is a break in trend, and we have finally succumbed," said Worth.

But it's not just the recent break in trend that has Worth worried. Worth noted that with its recent declines, Apple broke its long-term trend line that has been in place for the better part of a decade.

But Worth's chartwork reveals other troubling patterns. Apple's recent underperformance reveals a head-and-shoulders top — a bullish-to-bearish reversal — which would imply a move lower, said Worth.

All of these bearish patterns come as shares of Apple have exhibited poor strength relative to the market, said Worth. The tech giant is underperforming the Nasdaq, with the stock down almost 16 percent from its peak in comparison to the Nasdaq, which is down 6 percent.

"Sell Apple," said Worth.