Now that things look "as bad as can be" for Apple, there are no other reasons for the iPhone maker to underperform the broader market in 2019, and the equity looks cheap enough to upgrade, according to one Wall Street firm.

"We see limited further relative downside to the stock," New Street Research analyst Pierre Ferragu said in an investor note Thursday. "The macro environment has deteriorated, especially in China. A 20 percent shipment decline is not only our thesis. Based on CEO comments, we conclude Chinese consumer demand is very weak and took its toll as well."

He upgraded the shares to neutral from sell and set a $140 price target on the stock. That's still below where it finished on Thursday, at $142.19 per share.

Chief Executive Tim Cook said Wednesday that Apple sees fiscal first-quarter revenue of $84 billion versus a previous guidance of a range of $89 billion and $93 billion, a decline of about 7.6 percent. For investors, Apple's ability to generate revenue growth often plays a critical role in determining the higher the price they're willing to pay for its equity.

The New Street upgrade came as scores of other analysts slashed forecasts on the consumer technology company and downgraded the stock. Jefferies and Macquarie each threw in the towel and downgraded the stock to a neutral rating, while Goldman Sachs cut its price target to $140 from $182.

"We nevertheless expect the situation to stabilize in 2020 and EPS growth to resume," New Street's Ferragu wrote. "The stock is now trading close to 10x our 2020 earnings expectation, a historic low in absolute and relative terms, and see limited further downside to the stock."

Following the projected revenue miss, Apple shares dropped about 8 percent to $145.15 Thursday afternoon after ending the first day of 2019 at $157.92. Analysts expected revenue of $91.3 billion for the fiscal first quarter, according to the consensus estimate from FactSet. Apple blamed most of the revenue shortfall on a slowing economy in China in the second half.

Still, many analysts — including Ferragu — had expected weaker Chinese sales as the larger macroeconomic environment deteriorates both in Asia and around the globe.

"We were expecting the major negative surprise to be the March quarter," Ferragu added. "Reality is that Apple and channels saw the trend much earlier, ahead of the holiday season and adjusted shipments accordingly. We don't materially change our forecast for the March quarter and beyond."

New Street is a relatively small firm on Wall Street focusing on technology. Prior to joining the firm, Ferragu covered tech for Bernstein for 10 years, according to his website.