Molly's Game: Who Was Mr. X in Molly Bloom's Poker Games?

In the movie Molly's Game, there is a character called Mr. X, a celebrity who plays poker in Molly Bloom's games. Who was Mr. X? Which celebrities played?

Hollywood Flashback: In 2008, Molly Bloom Was Tinseltown's Poker Queen – The Hollywood Reporter

Molly's Game (2017) – Mr. Movie's Film Blog

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Molly's Game vs. The True Story of Molly Bloom

Molly's Game vs. The True Story of Molly Bloom

Molly's Game vs. The True Story of Molly Bloom

359- Molly Bloom TSC HIM & HER SHOW