Sometimes called delta EV, this metric describes the accuracy of a GTO solution. It's measured as the maximum aggregate EV that the solution can be exploited for. For example, if the value of playing some strategy is 5, but the opponent could adjust to exploit your weaknesses and reduce your EV to 4, then the Nash Distance is 5 - 4 = 1. A strategy with a Nash Distance of 0 is said to be at Nash Equilibrium.