Lagrave's blunder

In FIDE world cup, I watched a game of Kramnick.Here hia opponent did a Patzer mistake

Here is the game.

[Event "FIDE World Cup"]

[Site "Tromso"]

[Date "2013.08.28"]

[Round "6.3"]

[White "?"]

[Black "Kramnik, Vladimir"]

[Result "0-1"]

[WhiteElo "2719"]

[BlackElo "2784"]

[ECO "C45"]

1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Nxd4 Bb4 5. c3 Bc5 6. Be3 Bb6 7. Bd3 Nf6 8.

O-O O-O 9. Nxc6 bxc6 10. e5 Nd5 11. Bd2 d6 12. c4 Ne7 13. Qc2 Ng6 14. exd6 cxd6

15. Nc3 Qh4 16. Rae1 Ne5 17. Re4 Qh5 18. Be2 Qg6 19. Qd1 Bh3 20. Bf3 Bf5 21. Rh4

Bc2 22. Qxc2 Nxf3 0-1

Please tell.

In this level?

Patzer Mistake in the patzer variation (4.. Bb4+).

I guess it was because of time trouble. It was only a rapid game, and you can easily end up in time trouble there. 

4..Bb4 is good move in a scotch game.