Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...f5/4. Nc3/4...fxe4/5. Nxe4/5...Nf6/6. Nxf6/6...Qxf6/7. Qe2/7...Be7/8. Bxc6/8...bxc6/9. Nxe5


 * 9...O-O looks like the best developing move Black has, immediately bringing the rook to the open f-file. What could be better than that?
 * 9...Qe6 could be better than that. Catching the opposing king in the centre is half the fun of sacrificing pawns, and here 10.O-O?? would unprotect the White queen and so drop a piece to 10...d6.
 * 10.d4 is surprisingly popular given that it doesn't actually get out of the pin! (It does help develop a piece though.) Black has tried various moves to claim some initiative; Radjabov's choice is 10...Bf6, 10...O-O is also obvious, 10...a5 prepares ...Ba6 hitting the queen, 10...c5 immediately challenges the d-pawn.
 * Karjakin tried 10.Nf3 against Radjabov, which does get out of the pin. White loses castling privileges after 10...Qxe2 11.Kxe2 but can easily castle by hand with Re1 and Kf1.
 * Dominguez Perez tried 10.Nc4 against Fressinet, to similar effect.
 * 10.Qe3 is a radical solution tried by Frolyanov and Timofeev. Black has ...Ba6, ...Bf6 and ...c5 options after mutual kingside castling.