Former LSU running back Leonard Fournette on Wednesday signed a multi-year deal with Under Armour that a source tells ESPN is one of the most valuable endorsement contracts ever for an NFL rookie.

"We have a roster of athletes that we choose and we're never going to be that company that just collects athletes just to have the most," said Ryan Kuehl, the company's senior vice president of sports marketing. "We look for special people, who have the talent, the character, the story and the sense of purpose. Leonard Fournette fits that model."

Excited to join team @UnderArmour. Starting today we're going to do great things together. pic.twitter.com/8xNgzXVj6B — 7⃣ Leonard Fournette (@_fournette) January 18, 2017

Fournette will provide Under Armour with an NFL running back -- a position that is lacking in the company's portfolio. The shoe and apparel company is most known for quarterbacks Tom Brady and Cam Newton and wide receivers, including Julio Jones and Demaryius Thomas.

Fournette wore Under Armour in high school at St. Augustine in New Orleans and played in the Under Armour All-America game in 2014, where he announced his decision to go to LSU.

"I've always had a great relationship with Under Armour and it means a lot that a company wants me to wear their product and that I'm good enough to represent them," said Fournette, who turned 22 on Wednesday.

Fournette said that going with Under Armour means doing something different, just like his decision to go with Jay-Z's Roc Nation Sports to represent him. The deal closer? "Sitting across from Jay-Z," Fournette said. "That was crazy."

The pitch to land Fournette from Roc Nation came with high praise, something the marketplace seems to have bought into, at least with this first deal.

"When we met with Leonard, we told him we thought he was a once-in-a-lifetime running back and that the partnerships he had an opportunity to do with us would be historic," said Michael Yormark, president and chief of strategy and branding at Roc Nation.

Yormark said he couldn't disclose the Under Armour deal, but said that financially it fit the characterization of "historic."

Leonard Fournette rushed for 3,830 yards and 40 touchdowns in his three seasons at LSU. John Reed/USA TODAY Sports

Yormark said he already thinks of Fournette as a national brand, given his three years of exposure at LSU, and does not think the chatter over him skipping his bowl game will affect his client negatively.

"I think people understand the big picture," Yormark said. "They know why he chose not to play and they're not going to hold it against him."

After playing in 12 and 13 games in his first two seasons, Fournette only played in seven this past season due to injury. He still averaged 6.5 yards per carry this season, the mark he had last season in which he almost ran for 2,000 yards.

Kuehl said Under Armour plans to use Fournette to pitch a variety of products from training to footwear, lifestyle and connected fitness, with an immediate focus on the brand's NFL Combine Authentic line.

Fournette is expected to be taken in the top 10 picks of the draft.