Petite Combination in the Spanish opening

While studying opening theory, I came across what Capablanca called “Petite Combination”:

 White to move.
What's wrong with Black's last move Ra8-c8?
2rq1rk1/3nbppp/b2p4/pp1Pp3/1n2P3/1N3N1P/PP3PP1/R1BQRBK1 w - - 0 18

Solution: White plays 18.Nxa5! Qxa5 19. Bd2

the bishop established a pin that after a2-a3 will leave White with an extra pawn.

Looking at the Chigorin Variation of the Spanish Opening over the years, I noticed that the weakness of the dark squares on the queenside after Black's a6 and b5, highlighted by White placing his knight on b3 and bishop on d2, is a common theme. Here it is exploited in its purest form!