After 9.Bxb4 axb4 10.Nb1 Ra8 , followed by ...Ra2, White is under pressure.

Seizing the seventh rank with a clear initiative.

Preparing a2-a4 in order to clear the a-file for the white pieces.

Preventing Nc3-e4.

After 6...R8c7 7.Rc6!? the strong passed pawn speaks in White's favour.

Restricting Black's kingside pieces.

White later realized his extra pawn.

By attacking the bishop White gets ready for 2 Qc7, seizing the seventh rank.

1...Qa6 2.Qxa6 Bxa6 3.Rc7 h6 was preferable. White has still managed to seize the seventh rank, but he doesn't win a pawn as in the game.