(Reuters) - Super Bowl champion Rob Gronkowski this week will become the first pro athlete to launch a set of his own digital trading cards, telling Reuters he expects the rarest one to fetch “millions.” The Tampa Bay Buccaneers tight end’s cards are part of a wildly popular new type of digital asset known as a non-fungible tokens (NFTs). The Gronkowski NFT cards will exist only online, but blockchain technology allows the owner of each unique card to have it publicly authenticated, giving the owner bragging rights to the original even though the image can be copied. The technology has already made waves in the art and music worlds, where NFTs have changed hands for eye-popping amounts of money, including the sale of a 10-second video clip by artist Beeple for $6.6 million last month. The future NFL Hall of Famer, known as “Gronk,” said he grew up in a house filled with stacks of baseball and football cards and is thrilled to be part of the next era of collecting. “If you go back to my dad’s house and go into the closet, we’ve still saved every card,” Gronkowski said during a remote video interview. “I always was a big collector of trading cards. And now it’s super cool to be able to give my fans this opportunity and to be the first athlete out there to have a digital trading card.” While Gronkowski is the first athlete to release NFT trading cards, the NBA’s Top Shot website already allows users to buy and trade NFTs in the form of video highlights from its games. Last month, a user paid $208,000 for a video of a LeBron James slam dunk. Gronkowski’s cards will be up for sale on NFT marketplace OpenSea on Thursday. He expects significant interest in the crown jewel of the offering - a one-of-a-kind refractor card that celebrates all four of his championships. “The auction market is going pretty crazy right now,” he said. “I feel like it’s going to be in the millions of dollars.” To sweeten the deal, the winning bidder for the refractor card will also get to meet Gronkowski in person and attend a game as his guest. “As the first athlete, I feel like it’s going to hit the millions. I don’t see why not,” he said. “It’s going to go big.”