The New York Knicks pulled off the largest comeback in NBA Finals history Wednesday, and retail traders on Kalshi turned that miracle into roughly $22 million, most of it taken off Susquehanna International Group.

Market makers lost $22.4 million before fees on the game, while “takers,” mostly retail accounts, booked that $22.4 million in profit before fees and $20.6 million after.

Susquehanna, believed to be the largest market maker on Kalshi, reportedly absorbed the bulk of it, in what a source called its worst sports day on record.

The damage came almost entirely on the game-winner market.

The Knicks traded near 5% while trailing by 29 points in the third quarter, and stayed under 10% for more than 80 minutes of real time, so makers kept selling cheap contracts on a team that would storm back to win 107-106.

Large Errors For The Spurs

With the Spurs up 106-105 and 11 seconds left, De’Aaron Fox attacked the rim instead of running out the clock, the kind of human mistake it’s difficult for algorithms to price in. OG Anunoby blocked the layup, then won it with a tip-in in the final seconds.

The Spurs scored just 16 fourth-quarter points, and Victor Wembanyama missed two late free throws that would have made Fox’s error immaterial.

“I won’t confirm the exact loss, but it was a tough day,” Jeff Yass, the Susquehanna co-founder and a self-described former Knicks fan, told InGame. “I grew up a Knicks fan but at this size, I was conflicted.”

Record Day For Kalshi

The comeback helped drive Kalshi to its biggest day ever, with $872 million traded, narrowly beating Super Bowl Sunday. The surge extends Kalshi’s run as the U.S. market leader, with May volume up over 2,500% on the year, valued at $22 billion in its latest round.

The game-winner contract alone saw $171.6 million change hands, ranking among the ten most-traded markets in Kalshi’s history and generating $2.3 million in fees.

Why It Matters For Robinhood & Kalshi

Susquehanna, the desk that absorbed Wednesday’s loss, also makes markets on Rothera, a new, separate CFTC-licensed exchange that Robinhood Markets (NASDAQ:HOOD) and Susquehanna invested in last year. Robinhood now routes some event contracts there instead of Kalshi.

Robinhood once accounted for nearly 60% of Kalshi’s volume, reportedly down to about 20% by April. As it shifts World Cup and baseball contracts to Rothera, the retail flow behind nights like Wednesday is volume Kalshi may stop seeing.

Image: IMAGN