Ruy Lopez: Berlin Defense, Rio Gambit Accepted: what should White play?

In the Ruy Lopez: Berlin Defense, Rio Gambit Accepted (ECO C67), White faces a choice between the immediate strike d4 and the rook development Re1. While d4 is overwhelmingly favored in human practice, engine analysis assigns its top evaluation of +0.17 to Re1, directly targeting the undefended knight on e4. Either option allows White to challenge Black's central control while leveraging the secure position of the king.

The Main Practical Choice: 4. d4

The move d4 represents the standard approach, appearing in 77.9% of recorded games (266K recorded) with an engine evaluation of +0.13. By striking directly at the center, White opens lines for development while questioning Black's advanced piece. The illustrative engine continuation runs d4 Nd6 Bxc6 dxc6 dxe5 Nf5, leading to rapid piece exchanges and typical Berlin pawn structures.

The Engine Preference: 4. Re1

Although played in only 0.6% of games (2.0K recorded), Re1 earns the highest engine assessment at +0.17. The move places the rook onto the open e-file opposite the black king before committing central pawns. An illustrative engine line following this move proceeds Re1 Nd6 Nxe5 Be7 Bf1 Nxe5, demonstrating a controlled regrouping where White recovers material while preserving pressure along the file.

Alternative continuations

White occasionally employs other setups, though they yield lower evaluations. The queen moves Qe2 (evaluated at -0.04 across 13K recorded games) and Qe1 (evaluated at -0.10 across 1.2K recorded games) both target the e-file but block other pieces. A frequent human alternative is Bxc6, occurring in 17.5% of games (60K recorded). Finally, the flank option a4 registers at -0.20, with the illustrative line a4 a6 Bxc6 dxc6 Re1 Nd6.