I'll toss Apple if it doesn't let go of its iPhone crutch: Analyst

Apple v. the world
Apple v. the world   

Despite the buzz over its new watch and strong smartphone sales, Apple has under-performed the Nasdaq Composite Index since February 23, with shares only up 1 percent in comparison to the Nasdaq's 3 percent move.

With competitors like Google's new payment system and Xiaomi's Mi Band hitting the market in the near future, BGC senior analyst Colin Gillis says that Apple's dominance—and even his rating on the stockcould be in jeopardy. Recently, Gillis wrote that the tech titan's reliance on the iPhone could be "a liability as technology trends remain fickle."

In an interview on CNBC's "Fast Money" this week, Gillis explained that he's concerned about two trends he considers alarming: a lengthening upgrade cycle and a slowing smartphone market.

Gillis hinted that he may reconsider his hold rating on the stock if he's not wowed by Apple's Worldwide Developers Conference, which is set for June 8–12 in San Francisco.

Read MoreApple has a fix for the widespread iPhone shutdown glitch

Competition gets tougher

Since its 2007 introduction, the iPhone has made Apple money hand over fist. Fast forward several years, and a host of competitors are starting to get hip to its game—pressuring the company to maintain its edge, or fall prey to fickle consumers looking for the next best thing.

Read MoreHow the iPhone cold-cocked BlackBerry

Gillis' warning comes as the mobile device market appears to be losing steam. Vendors shipped a total of 334.4 million smartphones worldwide in the first quarter of 2015, up 16.0 percent from the first quarter of 2014 but down 11.4 percent from the fourth quarter of 2014, according to data from the International Data Corporation.

Shares of Apple have been hovering around the $130 level, despite reporting record second-quarter earnings.The strength in the results was driven by strong demand for the iPhone 6.

Why hasn't the tech giant's stock moved? One reason could be the stiff challenge Apple is facing from its existing competition. This week, Google announced Android Pay, an app used to make credit card payments on mobile devices which could directly compete with Apple Pay.

Simultaneously, Chinese device maker Xiaomi said the company will be launching online stores for the U.S. and Europe in early June—a challenge to iTunes.

As the top player in the smartphone market in China, "Xiaomi is absolutely a risk to Apple," said Gillis. As the price gap widens and functionality gap closes, consumers don't need to spend $800 on an iPhone when there are cheaper, high-quality phones on the market, he added.

According to Gillis, the real question investors should pose is whether there are other catalysts on the horizon to move Apple's stock higher.