Under Armour's CEO sent Nike's CEO a threatening card every Christmas - here's what it said

Under Armour CEO Kevin Plank had a special holiday message for Phil Knight, CEO and founder of Nike.

Plank sent a card to Knight ever year with the phrase "You will know our name," written in it, according to a new NBC interview with Under Armour's CEO.

While ostensibly a threat to Nike and its dominance, Plank says it "wasn't spiteful," but that when he was recruiting employees Under Armour, he employed an "us versus them" competitive mentality. Many told Plank that Under Armour "wasn't even on Nike's radar."

"To me, we were always on the radar. To me, were always in that game. To me, we're always in that fight," says Plank. The yearly holiday card was just Plank's way of making it clear that he and his company were coming for Nike.

NBC's full interview with Plank will air on Sunday on "Today with Willie Geist."