There's no denying it's been a frustrating few years for Under Armour (NYSE:UA) (NYSE:UAA) shareholders. The company has faced more than its fair share of staggering headwinds: a string of sporting-goods retailer bankruptcies; sputtering growth from its core North American business; revelations of (and changes to) its toxic male-dominated company culture; the more recent surprise resignation of Kevin Plank as CEO; and concerns over the outcome of a years-long accounting probe by the Securities and Exchange Commission and the Department of Justice.

I generally favor buying shares of businesses as they work from a position of strength -- winners tend to keep on winning, after all. But with Under Armour stock down around 60% from its late-2015 peak -- and off nearly 25% from last year's highs even as the broader markets surged to record levels -- I think now might be exactly the time investors should consider opening or adding to a position.

Digital world map, with charts indicating gains

IMAGE SOURCE: GETTY IMAGES.

For one, Plank remains Under Armour's executive chairman and "brand chief." And despite his missteps at the helm as CEO, I think the company can still benefit from his vision.

A crucial inflection point

I also believe the perspective of new CEO Patrik Frisk could be exactly what Under Armour needs right now. Formerly Under Armour's chief operating officer -- and the architect of a multiyear restructuring plan (which just finished its third year) to reduce costs, improve inventory management, and rightsize the company's infrastructure as it dealt with the slowdown -- Frisk is now positioned to spearhead an inflection point in Under Armour's longer-term growth trajectory.

During last quarter's conference call, Plank noted: "2020 will will be the first year since our transformation began that we will have the ability to put the right resources combined with the scale behind our brand marketing efforts."

Indeed, over the first few weeks of January, we've seen Under Armour begin to ramp up its newest ad campaign with the tag line "The Only Way Is Through" -- a fitting assertion considering the company's own persistent struggles.

The accounting probe remains a risk. But Under Armour says it has cooperated with every request from SEC and DOJ officials. It further continues to insist that the practices in question -- namely, alleged shifts in recorded revenue to make sales trends appear healthier -- were "entirely appropriate," and even commonly used in the broader retail industry.

Meanwhile, Under Armour has still managed to maintain its momentum overseas; international revenue grew a modest 5% year over year last quarter (up 8% at constant currencies) to $368 million, or roughly 26% of total sales.

But the more pressing tailwind for Under Armour stock could come from growth turning positive once again in North America (where sales fell 4% last quarter). This development could be imminent, judging by recent results from competitors like Nike (which just posted 5% quarterly growth in North America last month) and lululemon athletica (which saw domestic sales rise 21% in Q3, followed by an encouraging early release of its holiday quarter's results last week).

The key for investors, then, will be to make sure they're holding Under Armour shares before the benefits of its new brand marketing take hold, and before that North American inflection becomes evident. Once that happens, I see no reason Under Armour can't reclaim its status as a market darling.