Under Armour Inc. fell the most in almost three months after announcing the departures of two top executives, raising concern that the athletic-gear maker is losing management talent in key growth areas.

Chief Merchandising Officer Henry Stafford and Chief Digital Officer Robin Thurston will step down in July, the Baltimore-based company said Tuesday in a statement. Michael Lee, co-founder of the MyFitnessPal app, which Under Armour acquired last year, will take over the digital operations. Kip Fulks will lead merchandising on an interim basis.

The departures hit Under Armour -- which already was facing doubts that it can maintain its robust growth -- in two of the most important drivers of its expansion. Chief Executive Officer Kevin Plank has invested heavily to establish Under Armour’s presence in mobile applications that track physical activity. And Stafford was vital in growing Under Armour’s apparel business by getting its products into more stores. The changes also follow the departure of Chief Financial Officer Brad Dickerson, who left the company last year.

“While we think brand momentum remains strong, we see the confluence of these high-level departures, particularly in growth areas of the business, as a concern,” Jessica Schmidt, an analyst at KeyBanc Capital Markets, said in a note on Tuesday. Schmidt rates the shares sector weight, the equivalent of a hold

Under Armour dropped as much as 6.7 percent to $39.88 in New York, the biggest intraday decline since Feb. 8.

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