An AI-based comparative analysis of white’s decision strategies against 3...c6 in the Petrov Defense

Abstract

This study presents a comparative engine-based analysis of the unconventional continuation 3...c6 in the Petrov Defense after 1.e4 e5 2.Nf3 Nf6 3.Nxe5. In the master-level database checked for this study, no recorded examples of 3...c6 were found in the Lichess Masters explorer, indicating that the line remains practically unexplored in professional play. To evaluate its theoretical and practical status, three principal White continuations—4.Bc4, 4.d4, and 4.Nc3—were analyzed with Stockfish under fixed parameters (depth = 28, MultiPV = 1, hash = 256 MB, threads = 8). For each variation, the principal variation was followed through a fixed sequence of positions, and the resulting evaluations were normalized to White’s perspective. The results show that 4.Bc4 yields the highest mean evaluation for White (+1.15), 4.d4 gives the lowest average White advantage (+0.62), and 4.Nc3 occupies an intermediate position (+1.00). Standard deviation and a variance-based stability index remain low in all three lines, indicating structurally stable assessments rather than tactically erratic behavior. Overall, the findings suggest that 3...c6 does not equalize and leaves Black with a persistent positional disadvantage, although it is not immediately tactically refuted.