The owners of a top-tier Spanish soccer team had to move fast. Coming into the final game of the season, the club was on the brink of getting kicked down to a lower league, which would have meant millions in lost ticket and broadcast revenue.

So they turned to Kalshi, placing a multimillion-dollar hedge that wound its way through the insurance and commodity-brokerage world, in case the game didn’t break its way. In the end, the club squeaked by, losing its final game of the season by a narrow enough margin, 1-0, to keep its place in the top tier of La Liga.

But its prediction-market bet shows how these platforms are beginning to outgrow their YOLO beginnings and could one day underpin big parts of traditional finance.

On the other side of the Spanish team’s trade was Susquehanna, according to people familiar with the matter, which says it was the first quant trading firm to establish a dedicated prediction-markets trading desk. Susquehanna didn’t respond to requests for comment, but people familiar with the trade said the firm took home more than $1 million.

After this story came out, the team, Osasuna, confirmed some aspects of the trade but said it took out a standard insurance contract without any knowledge of what happened after that. It told me it “did not place a bet,” nor have a “direct relationship with Kalshi.”