A collapsing share price has sent Under Armour (NYSE:UA) (NYSE:UAA) stock to its lowest level since 2009. That slump could make the sports apparel specialist an attractive long-term buy -- assuming management's rebound strategy succeeds. On the other hand, Under Armour may be facing years of additional market struggles ahead.

Below, we'll look at Under Armour's main revenue sources and how they might contribute to a turnaround for the business.

A jogger drinks out of a water bottle.

Image source: Getty Images.

Selling to retailers

The majority of Under Armour's sales occur through its wholesale channel, which includes sporting goods chains, department stores, and specialty retailers. Last year that segment accounted for 65% of the business.

While this setup is an efficient way for Under Armour to quickly distribute its products around the world, it comes with important drawbacks. Retailers may yank back their purchase plans on short notice, for example, or halt them altogether during periods of financial stress. These chains may also choose to slash product prices, hurting Under Armour's profitability and branding in the process.

Like rival Nike (NYSE:NKE), Under Armour is responding to these challenges by pouring investments in a direct-to-consumer sales channel that includes its e-commerce site and a network of brand and factory store locations. This division was responsible for 31% of the business last year and, since these sales are both more profitable and faster-growing, Under Armor is working to push that proportion higher over the next few years.

Focused on the United States

In contrast to Nike, which gets just 47% of sales from the U.S. market, Under Armour remains a predominantly U.S.-based business. Revenue from its home market was $4 billion last year, or 83% of the total. Under Armour's next biggest geographic segment was Europe, at 6.9% of sales.

CEO Kevin Plank and his executive team want to extend their brand deeper into outside markets. "We believe the trend toward performance products is global," management explains in its 10-K report, "and [we] plan to continue to introduce our products...to athletes around the world."

Chart showing spiking international sales.

International sales in millions. Chart by author. Data source: Under Armour filings.

The good news is these international divisions are seeing impressive growth, with revenue spiking 57% in the most recent quarter. However, the retailer isn't likely to see anything approaching Nike's geographic diversity for many years. Under Armour's U.S. business was 91% of the total in 2014 and 87% in 2015 before dipping to 83% last year.

Apparel and footwear

Under Armour's product mix is split between apparel, footwear, and accessories. Its apparel category is by far the biggest, though, responsible for $3.2 billion of sales, or 67% of the business. Footwear comes in second at 21%, and accessories account for the rest.

The footwear segment is growing faster than any of the retailer's other categories, yet it has a long way to go before it matches Nike's 65%. Athletic shoes tend to carry lower profit margins than performance apparel, and so the relative strength of the division has contributed to Under Armour's profitability decline. The retailer still beats Nike on this metric, but the gap between them has closed over the past few years.

NKE Gross Profit Margin (TTM) Chart

NKE Gross Profit Margin (TTM) data by YCharts.

Under Armour intends to continue pouring resources into expanding its footwear division. That focus will likely push profitability even lower over the short term. At the same time, the retailer's relative lack of geographic diversity leaves it highly dependent on a weak U.S. market. In fact, management recently lowered its full-year sales growth guidance to 10%, which isn't far from the high double-digit gain that Nike is projecting.

Before the last few quarters, investors had been used to seeing Under Armour grow at roughly twice its current pace even as it expanded earnings at a healthy clip. But recapturing those robust operating trends isn't just about connecting with customers again. For a real rebound to take hold, Under Armour must also execute around the slow work of diversifying the business into new geographies and sales channels.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.