Sales in 2019 are forecast by the company now to be up 3 to 4 percent, with results "relatively flat" in North America. Analysts, however, were expecting growth of 5 percent.

During an annual meeting with investors, Under Armour narrowed its earnings outlook for fiscal 2018 and now is calling for adjusted earnings per share to fall between a range of 21 to 22 cents, compared with a prior range of 19 to 22 cents. Looking to fiscal 2019, it said earnings per share are expected to fall within a range of 31 to 33 cents, while analysts were calling for 35 cents, according to a poll by Refinitiv.

Under Armour 's stock plunged more than 10 percent Wednesday as Wall Street was disappointed by the retailer's financial targets, especially in the U.S., where the company has been struggling to regain lost momentum.

From 2020 to 2022, Under Amour is now calling for low single-digit revenue growth in North America, on a compounded annual basis. It's then predicting low single-digital revenue growth in the U.S. in 2023, with international segments by that year making up roughly 40 percent of sales.

Evercore ISI analyst Omar Saad called Under Armour's targets for a rebound in North America "more modest" than expectations, as regions like China and Asia Pacific start to fuel growth.

"Noteworthy is that 2019 will be the last year of the 'protect the house' transformation phase, suggesting Under Armour anticipates 2019 to be somewhat of another investment year, and the inflection to more meaningful growth and margin expansion won't begin until 2020," he added in a note issued to clients. Another concern among the financial community is continued pressure on profits, but Under Armour has said its move away from off-price channels should help relieve some of that.

Under Armour shares closed Wednesday down near 10.5 percent, having rallied more than 50 percent so far this year. The company has a market cap of about $9 billion, compared with that of rival Nike, which is more than $117 billion. Yoga pants maker Lululemon, which is also starting to target men and thereby threatening Under Armour, has a market cap of $16.2 billion. Its shares have rallied more than 55 percent this year.

Analysts and investors remain skeptical Under Armour will be able to continue to grow in the U.S., despite the company's lofty expectations. The market remains highly competitive, with names like Nike, Adidas, Fila and Outdoor Voices taking a greater share of shoppers' dollars. It's also been plagued by bankruptcies of wholesale retailers like Sports Authority.

"We know there will continue to be some contraction in this space," Under Armour's president of North America, Jason LaRose, said during an annual meeting with investors. "That's OK. We're planning for it."

Nomura Instinet analyst Simeon Siegel said sales in North America, which have been primarily fueled by apparel in past quarters, "may have capped." He added the company could benefit from "cleaning up its product margins" and selling more sneakers and clothing directly to consumers.

There's also mounting concern around Under Armour's recognition by consumers as only a "gym-wear brand" that sells sweat-proof shirts and shorts, NPD Group analyst Matt Powell told CNBC. Analysts wonder if the company will be able to pivot away from that.

"Under Armour must shift from being a performance-driven brand to a sportswear brand," Powell said. "True performance wear is shrinking," he said, because athleisure retailers like Lululemon and Athleta are surging in popularity.

LaRose said Wednesday the company will focus primarily on footwear and women's items, where there's a larger opportunity to grow. With 180 stores spread across the U.S. and Canada, LaRose said Under Armour will continue to target those consumers who play sports, but also that the segment's goal it to "fuel international ambitions."

Under Armour also has been working on cutting excess merchandise in stores and warehouses. It said inventories by the end of 2018 should be down a mid-single-digit percentage rate, which would be better than a prior range of flat to down slightly.

Meanwhile, with tensions running high amid U.S. trade negotiations with China, which could result in more tariffs imposed on goods like apparel, Under Armour told investors it plans to source just 7 percent of its products from China by 2023, compared with 18 percent today.

"We expect to continue to have production in China," Colin Browne, chief supply chain officer, said. "It's important for us to continue to have production in China."

Though its stock has rallied in 2018, Under Armour has watched its shares fall nearly 80 percent from their high in September of 2015 through the middle of last year.