The sound of shuffling stacks and splashing piles of colorful chips filled the cavernous poker room of the Rivers Casino. It was noon on a Wednesday, and on one side of the hall, dozens of men at a handful of tables were peering at their cards, placing bets and taking one another’s money. On the other side sat two players, roped off from the rest. They were carefully deploying sophisticated poker strategies and tactics, drawing on the sum of human knowledge about the game. Yet they held no cards and stacked no chips.