By almost any measure, Fitbit dominates the market. Its share of the high-tech wearables category, which includes everything from simple trackers to thousand dollar smartwatches, hit 25% last quarter, almost equal to its next three competitors combined, according to International Data Corp.

But this week, Fitbit conceded that its sales growth in the all-important upcoming holiday quarter will tail off to almost nothing. Last year, sales jumped 92% in the fourth quarter.

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With Fitbit’s stock price in free fall, analysts and investors are suddenly questioning how the company can get growth back on track. Some doubt that the market for fitness trackers is as big as originally thought.

“Given that Fitbit is about the only big player in the dedicated fitness device market, they really ought to be doing very well,” said Jan Dawson, chief analyst at Jackdaw Research. “The fact that they’re not is a sign that this is as much about the market as it is about Fitbit. And that’s a worry because Fitbit doesn’t really have any other businesses to go after.”

Smaller competitors like Garmin (GRMN) and Polar have done better but in a much smaller niche, mostly focusing on hardcore athletes. And Garmin, which also sells GPS devices for cars, planes and boats, isn’t expecting to grow sales much in the fourth quarter, either. Polar isn’t public and doesn’t disclose its financial results.

A year ago, when Apple (AAPL) introduced its first smartwatch, some saw the device as a major challenge for Fitbit. But the Apple Watch has hardly taken the market by storm, with sales sinking dramatically ahead of this year’s series 2 upgrade.

Fitbit (FIT) CEO James Park maintains that the problem isn’t coming from the competition. While 20% of U.S. adults already own a fitness tracker, two-thirds of all adults say they care about health and fitness and own a smartphone, he says.

“We feel that our growth opportunity in the U.S. is tackling that gap of about 46%,” Park said on a call with analysts this week. “And over time, methodically through new form factors, features, et cetera, we feel we’re in a good position to tackle that gap.”

Analysts are less convinced that the market’s untapped potential is nearly as large. After all, Fitbit already sells a wide array of products, ranging from the $60 Zip, a simple tracker, to the $250 Surge, which includes many of the features of a smartwatch. There’s not much more space for Fitbit to expand at either end of the price range, with cheap Chinese trackers on sale for $25 and Apple’s watch now starting as low as $270.

“Many people out there have overestimated the market size for wearables and most importantly have overestimated the need for them,” said Carolina Milanesi, an analyst at Creative Strategies. “Consumers still need to be convinced that they should invest money in these things that for many replicate what a smartphone can do.”

Park has also said that Fitbit needs to revamp its new product strategy to attract new buyers and convince current users to upgrade. This year, Fitbit released two new models in August, not exactly the height of shopping season. In 2017, Fitbit will offer different form factors and add new features and functionality, Park said, without getting more specific.

But perfecting new products isn’t easy, as Fitbit’s own troubles this year manufacturing its new Flex 2 band demonstrate. So until sales actually pick up, the market will remain skeptical.

(Update: This story was corrected on November 6 to note that Fitbit had manufacturing problems with the Flex 2 band.)