Of the big technology stocks, Apple is the most concerning, veteran technology investor Paul Meeks told CNBC on Thursday.
"Of all the FAANGs, the one I am frankly most worried about is Apple," Meeks said on "Power Lunch." The ecosystem "is all based on the number of iPhone users, and we are seeing a slowdown in the iPhone and the whole global smartphone market."
Meeks' comments come amid big gains in the technology sector.
Amazon's stock hit $2,000 per share for the first time just after market open Thursday, marking a major milestone in its climb toward a $1 trillion market valuation. At $2,020, the stock would need to gain just $30 per share in order to reach the 13-digit market cap.
Apple hit a market cap of $1 trillion in early August, becoming the first publicly traded U.S. company to reach that valuation.
FAANG is an acronym for the market's top-performing performing tech stocks, Facebook, Amazon, Apple, Netflix and Alphabet's Google. It was originally FANG when CNBC's Jim Cramer first coined the term as it did not include Apple.
Meeks, who is chief investment officer and portfolio manager at Sloy, Dahl & Holst, said he likes the growth outlook for Amazon, especially from its cloud computing subsidiary Amazon Web Services.
"Momentum continues, particularly in Amazon Web Services," Meeks said. "And we know Jeff Bezos is ruthless and has done a good job disintermediating a lot of noninternet industries, and I expect that to continue."
Apple, however, worries him.
Last quarter, iPhone sales were essentially flat and slightly missed sales estimates. And while pricier iPhones have helped maximize profitability out of a flattening user base, most bull cases are built on climbing services revenue. But Apple has a walled-garden approach to its hardware and software, so Meeks said iPhone sales could impinge the growth of services revenue.
Meeks is worried about Apple at $228 per share because "the bulls on this story have been latching onto the growth of the services business. Now that business is growing robustly ... but what folks don't realize is the services offerings within Apple — they are not sold a la carte."
"What happens with an [iPhone sales] lag is you will have a slowdown in the services business, because they are tied at the hip," he added.
Despite his reservations, Meeks isn't selling his core stakes.
With technology stocks trading at such high valuations, Meeks said he would probably recommend taking some money off the table — or at least not putting in any fresh money. Personally, he said is going to continue holding core stakes in some of the FAANG stocks.
"I would rather buy on a dip, because all these stocks, no matter how well regarded they are, or what I think about them fundamentally long term, will have a bad day. They are just very volatile names," Meeks said.
Apple did not immediately respond to CNBC's request for comment.
Disclosure: Paul Meeks' firm Sloy, Dahl & Holst has positions in Amazon and Apple.