After 1. e4 e5 2. Nf3 Nc6 3. c3 d5 there is also 4. d3 with a reverse Philidor from the Pirc move order (1. e4 d6 2. d4 Nf6 3. Nc3 e5), wich is trash but the player who is willing to do it probably has a lot of experience in that position and knows well the pawn structure.