Why 9...Bb6 in the Ruy Lopez, Wormald (Alapin) attack (C77)

I'm playing black in a Ruy Lopez game and White has played the Wormald (Alapin) attack.

After searching opening databases, it seems that Grandmasters usually play 9...Bb6 here.  But I don't understand the reason for it since 10. d4? doesn't seem to be a possibility. Can somebody help me understand this position better?

Thank you

I'm afraid chess.com rules dictate that we can't tell you, at least while the game is in progress.

I'm sure people will be happy to discuss with you after the game. (Or later on, if the game follows a different route.) While the game is in this exact position, we cannot do anything to help you.

Oops...thank you for letting me know. I'll repost after the game is over. Thank you.

OK my game is over...please read me original post above....thank you.

if you did not ready dont play ruy lopez

I don't play the Ruy, but perhaps black wants to play ...Na5 and ...c5?

That's not possible with Na5 first, because then ...Na5 Bc2 Bb6 b4. Perhaps.