The previous two games might not be all that important from a theoretical point of view, but the next two certainly are. Peter Svidler's handling of the so-called Perenyi Attack may well turn Black players off 6...e6 altogether. Which means we'll probably be seeing more practical tests of Kasparov's favourite 6...Ng4. Svidler's most important novelty was introduced in his game against Gelfand:

View annotated game: Svidler - Gelfand

Svidler (2689) - Gelfand (2681)

Biel (4), 2000

1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Be3 e6 7.g4 e5 8.Nf5 g6 9.g5 gxf5

10.exf5!

With his seventh move, White pretty much signalled that he was playing for an all out attack, so the fact that he's willing to sacrifice a piece (or more) to maintain the initiative, should come as no surprise.

10...d5 11.gxf6 d4 12.Bc4 Qc7 13.Qd3 dxe3

13...dxc3 has yielded better practical results, but this really doesn't change the flavour of the position. Black's hair is on fire any way you look at it.

14.0-0-0 exf2

15.Bxf7+!

In for a penny, in for the whole check book! I don't think White can do without this second piece sacrifice, since he needs to smoke Black's king out to continue the assault.

15...Kxf7 (15...Qxf7?? 16.Qd8 mate) 16.Qd5+ Kxf6 17.Ne4+ Ke7

18.f6+!

Amazingly enough, this move has never been tried before! White used to continue with Nd6, but Van Wely managed to put this move under a cloud in his encounter with Topalov in this year's Frankfurt Masters. This game continued: 18.Nd6 Bh6+ 19.Kb1 Kf6 20.Rhf1 Rf8 21.Rxf2 Nc6 22.Qc4 Kg7 23.Rg1+ Kh8 24.Rfg2 Bg7 25.Rxg7 Qxg7 26.Rxg7 Kxg7 27.Qg4+ Kh8 and Black had escaped the attack with a substantial material plus.

18...Ke8 19.f7+ Ke7

Last chance for 19...Qxf7?? 20.Qd8 mate.

20.Qd2

20...Qc6

20...Qb6 was suggested by American GM Lubosh Kavalek, and this is also what our German friend Fritz wants to play, but I think Black's position is beyond salvation at this point. Of course, if you have a lot of spare time on your hands, you can move up to the mountains and spend the next couple of years trying find a way out for Black. Who knows? Maybe there is one!

21.Qg5+ Kxf7 22.Rhf1 Bc5 23.Nxf2 Nd7 24.Ng4+ Ke8 25.Nxe5 Qe6 26.Rfe1

Yes, White is two pieces down, but all his remaining firepower is now aimed at Black's king.

26...Nf6

26...Rg8 must have been a better try, but Black's future still looks pretty grim after 27.Qh5+ Rg6 28.Nxg6 Be3+ 29.Kb1 hxg6 30.Qh8+ Nf8 31.Rd3 . White is winning back most of his material, and the attack will continue with undiminished force.

27.Nd3 Be7 28.Rxe6 Bxe6 29.Re1 Nd7(?)

A blunder, but Black was dead anyway. Gelfand resigned before Svidler could play Rxe6. 1-0

In a must-win situation in the penultimate round, Dutch adventurer Loek Van Wely invited Svidler to play the same variation, but Svidler demonstrated the versatility of White's position by employing a more "positional" piece sacrifice. In this line, Black is spared the dubious pleasure of having his king chased around the board with an axe, but his position might still be too hot to handle:
Svidler - Van Wely