Even according to players is a very old term from used in the 50's to describe any given team or single person the ability to win or lose when it comes to playing a game. It may also refer to a person in a group of friends who for whatever reason is unable to grasp the subject of the conversation. It was a polite way to say that someone was stupid.
The gang were all playing a game of cards when Billy walked up and asked who was winning. The gang replied that it was even according to players because "stupid Sam" was one of the players.