Exchange Variation, Keres Variation

The Keres Variation replaces the usual 5. O-O of the Exchange Spanish with 5. Nc3, guarding the e4-pawn with a piece. With e4 covered, the answer ...Qd4 no longer refutes a capture on e5, so a real threat to the black pawn appears. The difference from the Normal Variation is that White's king stays in the center, which changes the value of Black's pin. After 5...Bg4 the bishop can be harassed without risk to a castled king: 6. h3 Bh5 7. g4 Bg6 8. Nxe5 wins a pawn and gives White a modest edge.

The most frequent reply is 5...Bd6, which protects e5 and keeps the queens apart, with 5...Bg4 and 5...f6 next in popularity. After 5...f6 White can head for an endgame with 6. d4 exd4 7. Nxd4 c5 8. Nde2 Qxd1+ 9. Nxd1, which is level, or choose the quieter 6. d3, the Romanovsky Variation. The engine considers the position equal and lists ...f6, ...h6 and ...Qd6 as its preferred moves. In online play the results are close to even, and White scores slightly better.