MMA training has brought tech billionaire Mark Zuckerberg face to face with one of its most brutal truths: injuries.

Zuckerberg, who has been training for and engaged in talks about competing in a real MMA fight, says he suffered a torn ACL while on the mats. Friday, Zuckerberg shared photos from his hospital bed after undergoing surgery. The Facebook founder was preparing for a fight to take place early in 2024, but will have to adjust the timeline for his potential MMA debut as he recovers from a serious injury.

“Tore my ACL sparring and just got out of surgery to replace it,” Zuckerberg wrote on Instagram. “Grateful for the doctors and team taking care of me. I was training for a competitive MMA fight early next year, but now that’s delayed a bit. Still looking forward to doing it after I recover. Thanks to everyone for the love and support.”

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Zuckerberg, 39, has made his fighting intentions clear over the past year. He sat cageside at an event at the UFC Apex, while also hyping up a potential clash against fellow tech billionaire Elon Musk. The initial wave of talks of a bout against Musk fizzled, and Zuckerberg was in the process of finding a new opponent before the injury.

“Maybe next year. Not Elon, but someone,” Zuckerberg told The Verge in September about his potential MMA debut. “I want to keep competing, but I just need to find someone.”

Beyond witnessing fights up close as a fan, Zuckerberg has been putting real time in on the mats. In July, Zuckerberg posted a few photos from a training session with UFC featherweight champion Alexander Volkanovski and former middleweight champion Israel Adesanya.

Zuckerberg has also been honing his BJJ skills under the tutelage of Dave Camarillo, and recently was promoted to blue belt. He competed in his first tournament earlier this year, where he won first place in no-gi and second in gi at BJJ Tour Silicon Valley.