1.e4 e5 2.Nf3 Nc6 3.Bb5 f5 A surprise. In the past Naiditsch hardly ever played the Jaenisch-Schliemann Gambit with black. Though he has excellent results with White against this system.
4.Nc3 [Another important line, which was topical lately, is 4.d3 fxe4 5.dxe4 Nf6 6.0-0 Bc5 7.Qd3 ]
4...fxe4 5.Nxe4 Nf6 6.Nxf6+ Qxf6 7.Qe2 Be7 8.Bxc6 bxc6!? [The alternative direction is 8...dxc6 9.Nxe5 Bf5 ]
9.Nxe5 [A more principled move is 9.d4! where 9...exd4?! (9...Qg6 with a sharp play) 10.Bg5 Qe6 11.Qxe6 dxe6 12.Bxe7 Kxe7 13.Nxd4 is better for White.]
9...0-0 10.0-0 Qe6 11.Re1 Bc5 12.Nf3 Qxe2 13.Rxe2 d6! It is very hard for White to use his extra pawn.
14.d3 [Possibly White should prefer 14.d4!? Bb6 which was tested in several games.]
14...Bg4 15.Be3 Bb6N [After 15...Bb4 which was played before, White maybe can try 16.c3 (16.a3 Ba5 17.b4 Bb6 18.Bxb6 axb6 19.Re7 Bxf3 20.gxf3 Rf7 21.Rxf7 Kxf7 22.a4 c5! was OK for Black in Leko-Radjabov, Monaco 2007.) 16...Ba5 17.d4!? and if 17...Bb6 18.c4 threatening with c4-c5!. Curiously, both Efimenko and Naiditsch were unaware of the Monaco game.]
16.Bxb6 cxb6!? 17.Re3 Bxf3 18.gxf3 Rf6 19.Rae1 Raf8 20.Re6 [After 20.Kg2 Rg6+ 21.Kf1 Black can play 21...Rh6 (though 21...Rgf6 22.Ke2 Rh6 23.Rh1 does not look too dangerous for him either.) ]
20...Rxf3 21.Rxd6 Rxf2 22.Rxc6 h5 23.Rc7 R8f4!? [Or 23...h4 where 24.Ree7 Rf1+ 25.Kg2 R8f3 26.Rxg7+ Kh8 27.Rh7+ Kg8 28.Rxh4 R1f2+ is a draw.]
24.Re4 [Playing for a win by 24.h3 is unsafe for White: 24...h4 and Black has attacking possibilities such as ...R2f3 at some point.]
24...Rf1+ Now the game ends as the white king cannot escape from perpetual check.
25.Kg2 R1f2+ 26.Kg1 Rf1+ 1/2-1/2