Classical Variation, Burn Variation

The Burn Variation, named after Amos Burn and classified as C13, meets the threat of 5. e5 with 4...dxe4, removing the pawn that would otherwise hit the pinned knight. Black releases the central tension much as in the Rubinstein (3...dxe4), but only after White has committed the bishop to g5, so the exchanges that follow tend to leave Black with the bishop pair. White nearly always recaptures with 5. Nxe4; 5. Bxf6 and 5. f3 are rarer and have scored better for White on Lichess. The main line runs 5...Be7 6. Bxf6 Bxf6 7. Nf3 O-O, with 7...Nd7 as an alternative. Black's position is compact, and the two bishops offer dynamic counterweight to White's well-placed knight on e4. Evgeny Bareev long favored the line, and among elite players it is the choice most often seen against 4. Bg5.

The Morozevich Line, 6...gxf6, played by Alexander Morozevich and Gregory Kaidanov, accepts a damaged kingside in exchange for activity, with Black following up with ...f5 and ...Bf6. Another Rubinstein-like approach is 5...Nbd7 6. Nf3 Be7 7. Nxf6+ Bxf6. The engine rates the position after 4...dxe4 as roughly balanced.