Dive Brief:

• Under Armour has snagged yet another major sports figure to boost its athletic gear, signing a 10-year extension with Washington Nationals star right fielder Bryce Harper that sources told ESPN could be the largest endorsement deal in history for a Major League Baseball player.

• Under Armour has had an endorsement deal with Harper for five years, and its first Harper signature cleat, the Under Armour Harper One, launches in July. 

• The deal adds to Under Armour’s impressive endorsement roster, which also includes Golden State Warriors star shooting guard Stephen Curry, who is signed through 2024, and golf phenom Jordan Spieth (signed through 2025).

Dive Insight:

In reporting strong Q4 sales earlier this year, Under Armour CEO Kevin Plank called attention to the company's ongoing partnership with Stephen Curry, the NBA's reigning Most Valuable Player, saying that his signature basketball shoes helped fuel a 95% increase in footwear sales.

“We started by redefining the sports apparel industry through performance fabrics and today we are raising the bar for what athletes expect across all of their health & fitness needs,” Plank said in a statement at that time. “Our footwear business, driven by the outstanding success of our signature Curry basketball line, will deliver new iterations of signature product across premium price points and distribution throughout the year.”

But last month Morgan Stanley apparel and footwear analyst Jay Sole called Under Armour's huge North American footwear sales “unsustainable,” saying its continued growth would instead merely be “solid,” and added that its fiscal 2015 triple-digit running footwear growth was largely due to price cuts that outpaced its rivals.

Still, if there’s a better way to build brand awareness and validate performance features in sports gear than with high-profile endorsements from top athletes, the sports retail world has yet to find it.

In addition to Curry, Spieth, and Harper, Under Armour now boasts affiliations with National Football League MVP Cam Newton of the Carolina Panthers, New England Patriots quarterback Tom Brady, Los Angeles Dodgers pitcher Clayton Kershaw, San Francisco Giants catcher Buster Posey and Olympic swimmer Michael Phelps—in short, many of the most popular and celebrated athletes in American professional sports. Under Armour's endorsements also include the American Ballet Theatre's first-ever African-American principal dancer, Misty Copeland.