Berlin Defense, Anti-Berlin Variation

4. d3 avoids the 4. O-O Nxe4 complex and the Berlin endgame entirely. It steers the game toward slower Spanish structures in which d2-d4 comes later and at the cost of a tempo. Because e4 is now protected, Black has to address the threat to e5. The main reply, 4...Bc5, chosen in nearly half of the games, answers 5. Bxc6 dxc6 6. Nxe5 with 6...Qd4, which hits the knight and f2. White usually plays 5. c3, taking d4 away from the queen; 5. O-O and 5. Be3, the Kaufmann Variation, are the alternatives. 4...d6 defends the pawn directly but leaves the king's bishop in a passive role on e7. White can then choose between 5. Bxc6+, the Anderssen Variation, and 5. c4, the Duras Variation.

4...a6 is frequent in online play but loses a pawn to 5. Bxc6 dxc6 6. Nxe5, since ...Qd4 no longer forks anything, and White scores well after it. 4...Ne7, the Mortimer Variation, leaves e5 as bait. After 5. Nxe5 c6 6. Bc4 Qa5+, the queen checks and wins the knight, a sequence known as the Mortimer Trap. The engine rates the starting position as roughly balanced.