Under Armour has a sneaker deal with the best basketball player in the world. It pulled in nearly $4 billion in revenue in 2015 and recently overtook Adidas as the second largest sportswear company in the U.S. 

But it looks like it just lost a key member of its design team. According to sneaker blog Nice Kicks, senior vice president of design Dave Dombrow is jumping ship--to Nike, the number one sportswear seller in the world. 

Dombrow was Under Armour's top sneaker designer. He led development on Steph Curry's line, released February 2015. Nationwide sales of the shoes have soared along with the Golden State Warriors guard's shooting ability and popularity. Earlier this month, Morgan Stanley projected that Curry's line would overtake that of LeBron James in U.S. sales by the end of this year, reaching $160 million. Sales of James's sneakers are projected to hit $150 million.

The Curry basketball shoes designed under Dombrow are marked by high tops--essential ankle support for players like Curry who start and stop on a dime--and flashy colors. The sneakers, as well as some of Under Armour's running shoes, use a material called SpeedForm that forms to the foot and provides extra cushioning around the ankle and heel.

Curry can be seen during games wearing his sneakers in the Warriors' blue, gold, and white. The line offers everything from a classic black and white look to a swirl of pink, purple, green, and teal--all with Curry's initial imprinted on the tongue. The Curry Two, released this past October, helped sales of Under Armour sneakers as a whole climb by 95 percent in 2015.

In February, an Inc. cover story highlighted founder Kevin Plank's quest to overtake Nike as the world's biggest sports apparel retailer. The Baltimore-based company recently spent nearly $1 billion acquiring health technology apps with the intention of integrating them into its clothing.

As per his non-compete agreement in his contract with Under Armour, Dombrow will have to wait a year before beginning design work with Nike. His new company's most popular sneaker line by a wide margin is that of LeBron James.