Billionaire Bill Ackman and organizers of a tennis tournament have been strongly criticized by former grand slam champions and social media after the hedge fund manager made his professional tennis debut, a match he ended up losing.

Ackman, who has a prominent social media presence on X, played with three-time grand slam doubles champion Jack Sock in the men’s doubles at the Hall of Fame Open – an event sanctioned by tennis’ world governing bodies, the ATP and the WTA, though CNN understands that the men’s side of the event is governed by ATP rules – on Wednesday where they lost in straight sets 6-1, 7-5 to Omar Jasika and Bernard Tomic.

The 59-year-old and Sock were vastly outplayed by their Australian opponents, coming second in almost every statistical measure in their match in Newport, Rhode Island.

Ackman had been invited to play by Sock, who had received a wild card entry to the tournament, which is a WTA 125 event and also sits on the ATP Challenger Tour, a lower-tier men’s tour focused at giving younger or aspiring players an opportunity to progress their careers.

Ackman – the founder and CEO of Pershing Square Capital Management and has a personal net worth of $9.5 billion according to Forbes – said it was a dream come true to play pro tennis just once.