The White knight is now the dominant piece on the board, crippling Black's game. The Black rook cannot go to d8, the obvious file for it, nor can it threaten the seemingly-backwards e3 pawn since the knight blocks that file, too.

A wasted tempo. The rook should go to h1 immediately.

Sharp play: Black creates a passer on the h-file.

Positional assessment: Black has a 1-pawn material advantage, and it is a passer with a rook behind it--Tarrasch would love that part. But an elephant is sitting on Black's passer; it is going nowhere. White's knight is patrolling all the squares in Black's camp worth having, preventing the Black rook from occupying d8, while also preventing the Black king from wandering over to protect the h-pawn and freeing the rook for other duty. The knight is also hitting c7, forcing Black to cover it. The Black bishop is relegated to little more than elder brother to the f-pawn and has no significant target in the White camp. White has a clear plan from here on: penetrate the Black position by advancing the king. Black can do little but mark time and watch it happen. Any attempt to break up the White queen-side by advancing Black pawns will fail without the support of the Black rook, which is tied down.

White can afford to ignore all pawn activity on the queen-side, as there is no breakthrough there.

Oops. This gives the White king too easy an entry into the Black camp; the c-pawn should stay put on c6 and cover d5. Better was probably shuttling back and forth with the bishop (c3 - e5). The text move allows White a tactical shot ...

Threatening Nf7+ forking the rook; Black must respond to this, and thereby allow White entry.

Alternatives were no better. E.g., 29. ... Rf8; 30. Nxh7, Rh8; 31. Ng5, RxRh6; 32. Nf7+ regains the rook and Black's bishop is useless against the knight. Or 29. ... Re8 or ... Kc6; 30. Nf7. The superiority of the knight here is evident.

Black can no longer hold all his weak pawns. White will regain his sacrificed material, and more.

Time to get rid of the dastardly knight! If instead 33. ... Bd2; then 34. Rxf6 and Black is in imminent danger of getting mated on the back rank.