More accurate is 3.Nf3 and only then 4.Qb3.
4...Nc6
The twin threats of ...Nxd4 and ...Nb4 are hard to meet.
5.Nf3
White objectively had to try something like 5.cxd5 exd5 6.Be3, meeting ...Nb4 with Rc1.
5...Nb4
Now Black should be winning, but the fun is just about to start!
6.e4
White's only try.
6...dxe4 7.c5 a5 8.a3 exf3 9.axb4 Qxd4
Theory hounds take note! This move is a novelty. Davies (yes the GM!)-Hubert, Germany 1998, saw 9...axb4 10.Rxa8 Qxa8 11.Nb5 Qa1 12.Nxc7+ Kd8 13.Qd1 Qb1 14.g4 Bc2 15.Qd2 Kxc7 16.Bc4 Bg6 17.0-0 Qe4 18.h3 Bxc5? 19.dxc5 Kc8 20.Qd6 Nf6 21.Bf4 1-0
10.Be3 Qd7
A sensible retreat. Black's queenside would be deserted in case of 10...Qg4?! 11.g3 Nf6 12.bxa5.
11.bxa5 c6 Diagram
Here interesting was 12.Rd1 Qc7 13.Nb5 Qxa5+ 14.Bd2 fxg2 15.Bxa5 gxh1Q 16.Nc7+ Ke7 17.Nxa8 Kf6.
At the end of this line Black appears to be near winning, but 18.Nb6, threatening 19.Nd7+, may suddenly turn things around! A bizarre position.
12.Na4 Rxa5 13.Rd1 Qc7 14.g4 Bg6
Igor's swashbuckling play (and appearance) begins to affect Mezentsev's play. Why not take it all with 14...Bxg4? Black would be perfectly safe after 15.Qb4 Nf6 16.Nb6 Ra7.
15.Qb4 b5?!
Here 15...Nf6 looks safer.
16.Nc3 Be7
In anticipation of White's upcoming sac on b5 Black had some alternatives:
16...Ne7 17.Nxb5 cxb5 18.Bxb5+ Rxb5 19.Qxb5+ Nc6 20.0-0 Be7 21.Bf4 Qc8 22.Rd6 Bxd6 23.cxd6 0-0 24.Rc1 Be4; or 16...Nf6 17.Nxb5 cxb5 18.Bxb5+ Ke7. In all cases (including the game text) White's comp doesn't seem sufficient.
17.Nxb5 cxb5 18.Bxb5+ Kf8 19.Rd7 Diagram
19...Ra1+
In the diagrammed position Black was clear winning with 19...Qb6!! (Fritz!). Everything is hopeless:
20.cxb6 Bxb4+; 20.Rxe7 Qxb5; or 20.Rb7 Qxb7 21.Qxa5 Qe4.
20.Kd2 Qa5 21.Qxa5 Rxa5 22.Rb7 Ra8 23.Ra1!
An inspired try!
23...Rd8+
23...Rxa1 24.Rb8+ Bd8 25.Rxd8+ Ke7 26.Re8+ Kf6 27.Bd4+ wins for White.
24.Rd7 Rxd7+
Better was 24...Nf6 25.Rxd8+ Bxd8 26.Ra8 Ne4+! 27.Ke1 Ke7, and Black should be able to untangle.
After the text move Black soon finds himself in a terrible bind.
25.Bxd7 Be4 26.Ra4 Bd5 27.c6 Bd6 28.Kc3
A necessary quiet move to guard b4. If immediately 28.b4 then 28...Ke7 29.Ra8 Bxb4+.
28...Ke7 29.Ra8 Bxh2
29...Be5+!? looks like an improvement, but 30.Kd3 keeps it going for White with his queenside pawns ready to advance.
30.Bc5+ Kf6 31.b4 Kg5 32.Bd4 f6 33.b5 Kxg4 34.b6 h5
Here immediately giving up material with 34...Ne7 or 34...Bxc6 35.Bxc6 h5 was necessary. White would be clearly better, but not winning yet.
Diagram
35.b7?
A pity! White has a clear win with 35.c7! Bb7 36.Bxe6+ f5 37.Bxg7!
35...h4
Now Black is back!
36.b8Q Bxb8 37.Rxb8 h3?
Allowing a new set of queens to appear is a grave mistake. Vladimir should have been content with an ending with a bunch of pawns for a piece: 37...Bxc6 38.Bxe6+ ( not good is 38.Bxc6? h3 39.Bd7 h2 40.Bxe6+ f5 41.Rb1 Nf6! 42.Rh1 Kh3, and Black wins.) Kg5 39.Be3+ Kg6 40.Bxg8 Rh5.
38.c7
Now White is on top again!
38...h2 39.c8Q h1Q 40.Bxe6+ Bxe6 41.Qxe6+ Kh5 42.Qf5+ g5
Black would get mated in a spectacular fashion if he tried 42...Kh6 43.Rb1! (the point of 42.Qf5) Qh2 (or 43...Qg2 44.Rb4) 44.Be3+ g5 45.Bxg5+! fxg5 46.Rb6+ Kh5 47.Qg6+ Kg4 48.Rb4+ Kh3 49.Qf5+ Kg2 50.Qxg5+ Kxf2 51.Rb2+ Kf1 52.Qc1
43.Rb1 Qg2 44.Re1 44.Nh6 45.Qxf6 Rc8+
Black correctly gives up the piece. If 45...Rh7?, then 46.Re6 Kh4 47.Qg6 gets the job done.
46.Kd2 Qh3 47.Re6 Qf5 48.Qxh6+ Kg4 Diagram
49.Qg6?
Amazingly enough, this move lets the win slip away. 49.Ke3 Qf4+ 50.Kd3 Rc1 51.Qf6 should force an ending where White would face some technical difficulties, but would finally prevail.
49...Qa5+ 50.Kd3 Qb5+ 51.Ke4
Here the king is temporarily safe from checks, but it takes away the square his rook wanted to go to! The struggle continues with both players headed for time trouble again.
51...Rd8 52.Rd6 Re8+ 53.Re6 Rf8 54.Be3 Rf5 55.Bxg5?
Suicide. White had to play 55.Rd6, but there's no win in the pawn ending after 55...Qb1+ 56.Kd4 Qb4+ 57.Kd3 Rd5+ 58.Rxd5 Qb1+ 59.Kd2 Qxg6 60.Rxg5+ Qxg5 61.Bxg5 Kxg5 62.Ke3 Kf6 63.Kxf3 Kf5.
55...Rxg5 56.Qe8 Qe2+ 57.Kd4 Qxf2+ 58.Re3 Qd2+ 59.Kc4 Qd5+ 60.Kc3 Qa5+ 61.Kd4 Qc5+
0-1
Give both players credit for hanging tough and never giving up!