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?

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

Molly's Game - Metacritic

Review: The Big and Minor Stakes of 'Molly's Game' - The New York Times

The Truth About Player X From 'Molly's Game' - Airows

Film Reviews from Two Guys in the Dark: Molly's Game, Short Takes on All the Money in the World

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

Tobey Maguire is Player X? [Molly's Game] – did you blank it?

Aaron Sorkin's 'Molly's Game' Has Its First Trailer

Tobey Maguire Poker Story – Learn The Full Backstory Of Molly's Game