Ruy Lopez: Morphy Defense: what to play after Ba4?

In the Ruy Lopez: Morphy Defense (ECO C70), the position after e4 e5 Nf3 Nc6 Bb5 a6 Ba4 represents a critical juncture where Black must decide how to develop the kingside while addressing the pressure on the e5 pawn. The most statistically successful and popular continuation is Nf6, which is played in 54.4% of the over 22 million recorded games at this position and carries a slight engine evaluation of +0.26. This move initiates the Closed Defense or Open Defense variations, depending on White's subsequent choice between castling and other central reinforcements.

The main line with Nf6

The move Nf6 is the standard response, pressuring the e4 pawn and preparing for kingside castling. According to the data, the most common continuation follows the line Nf6 O-O Nxe4 d4 b5 Bb3, leading to the highly theoretical Open Ruy Lopez. By delaying the expansion of the queenside pawns until White commits the king, Black maintains maximum flexibility in the center.

Queenside expansion with b5

The second most frequent choice is b5, occurring in 29.6% of games (6.60 million recorded). This move immediately forces the a4 to the b3 square, as seen in the sequence b5 Bb3 Bb7 O-O Nf6 Re1. While this expansion gains space and prepares to fianchetto the light-squared bishop, the engine evaluation rises slightly to +0.32, reflecting the potential weaknesses created along the long diagonal or the a5 square.

Solid developmental alternatives

For players seeking different structures, d6 (7.2% of games) leads to the Steinitz Deferred, a solid but somewhat cramped setup evaluated at +0.40. Alternatively, Bc5 (5.6% of games) targets the f2 square directly, often leading to sharp tactical battles after Bc5 c3 Nge7 d4 exd4 cxd4. The least common major option is Be7, played in only 0.8% of games, which prioritizes immediate safety and a compact defensive shell.