 Black's most common reply is 2...Nc6, which usually leads to the Ruy Lopez (3.Bb5), Scotch Game (3.d4), or Italian Game (3.Bc4).If Black instead maintains symmetry and counterattacks White's center with 2...Nf6 then the Petrov's Defense results.The Philidor Defense (2...d6) is not popular in modern chess because it allows White an easy space advantage while Black's position remains cramped and passive, although solid.