Dive Brief:

• Under Armour’s shares fell the most in three months after Morgan Stanley analyst Jay Sole noted a market share decline made worse by poor sales among women. Shares fell 6.7% to $69.96, the biggest one-day drop since late September. 

• The company is slipping against rivals Nike and Adidas for the first time in three years and its average selling prices are falling at an accelerated pace, according to Sole. Under Armour’s stock rose 19% in 2015, among the best performances in apparel overall and its seventh straight year of increases. 

• The note comes as a surprise considering CEO Kevin Plank’s statements in recent years that the retailer would be boosting its merchandise offerings for women and amidst its head-turning “I will what I want” campaign aimed at women. “Both trends are more pronounced in women’s apparel, despite major marketing investment in this division last year,” said Sole, who cited data from SportScan.

Dive Insight:

Despite surpassing Adidas in the U.S. in 2014, Under Armour is still seen as the underdog in the athletic-gear sector. That’s because Nike remains number one, by far, outpacing Under Armour’s $3 billion in annual sales tenfold ($30 billion). But, almost like a jealous suitor, Nike for a while now has appeared to be closely watching how Under Armour is courting women. 

Under Armour went viral with its stunning and emotionally moving video of ballerina Misty Copeland, later signed supermodel Gisele Bündchen, and launched a massive global women’s marketing campaign last year. That campaign is part of the company’s effort to boost its $600 million women’s business to match or surpass its men’s business.

And beyond advertising, Under Armour CEO Kevin Plank said last year that the company is working on expanding its merchandise for women, to include more apparel that can be worn outside her underwear and outside the gym. Nike and Under Armour alike had concentrated a lot on sports bras and leggings, and less on the booming alth-leisure trend that has women wearing their gear to happy hour.

"We don't believe we played our best game yet. We don't think when you walk into a store you're getting the best version of Under Armour yet,” Plank said in a conference call to analysts last year. "I think you'll see Under Armour continue to take those steps towards being more relevant in more aspects of her life.”

The credit to uncovering women as a major force in sports apparel sales arguably goes to Lululemon, NPD Group sports retail analyst Matt Powell last year told Bloomberg. "When a brand can come out of nowhere and capture the kind of mindshare that they did, as quickly as they did, I think it woke everybody up,” he said.

Under Armour has apparently farther to go in appealing to women, and there’s still room to grow.

"The industry has under-served women for years," Powell told Bloomberg. "Only in the last couple of years have we seen brands and retailers really starting to give women equal weight."