The long streak at Under Armour of outstanding sales gains ended during the holiday shopping season quarter, as the sports apparel maker posted its results on Tuesday that sent its stock plunging 26%.

The athletic apparel maker based in Baltimore blamed a holiday season it called sluggish, a shift in retail landscape and miscalculations in merchandise for its sales between October and December of $1.3 billion, which while higher than the previous year by 12%, came up short of 20% quarterly gains and higher it reported for close to seven years.

Under Armour’s shares were hit hard by Wall Street when its results came up short of analyst’s expectations and it lowered its growth target for sales by 50% for 2017.

Its voting shares plummeted $7.45 a piece. Under Armour stock has not been this low priced since 2009.

The drop in stock prices ate into the net worth of Kevin Plank the founder of Under Armour. He is its largest single shareholder and is in control of the company through a type of stock that he possesses that has voting power that is 10 times higher that Class A shares.

Forbes has estimated that the billionaire saw his fortune drop 19% on Tuesday and is now $1.92 billion.

Plank said the lessons learned from Under Armour’s disappointing quarter could help keep the growth strategy of the company intact for the long-term.

The slowdown in sales growth was blamed by company officials on the competitive environment of discounting as the consumer shopped online rather that at malls and other standalone stores that represent much of the company’s business.

Analysts were expecting the company to post sales of more than $1.4 billion.

The company posted earnings that disappointed as well, saying that profit dropped from $105.5 million during the same quarter one year ago to $104.8 million.

Earnings per share dropped one cent to 23 cents, which was two cents less than average projections by analysts.

Under Amour lowered its sales growth outlook for the full year to between 11% and 12% from the range of the low 20s. While Under Armour reached a new record in 2016 for sales of $4.8 billion, which was 22% higher than 2015, it said it would reach sales in 2017 of close to $5.4 billion.

Analysts on Wall Street said that Under Armour lowering its expectations had taken investors by surprise, which they said also brought up questions about the sales target of $7.5 billion for 2018.

Get Analysts' Upgrades and Downgrades Daily - Enter your email address below to receive a concise daily summary of analysts' upgrades, downgrades and new coverage with MarketBeat.com's FREE daily email newsletter.