Bad move. Angel may be human and injured, but losing the demon within doesn't mean he's lost all those centuries of experience that he gained while he was still one. She rushes him and he moves to catch her off balance and counteract her would be assault, to use her momentum and lower center of gravity against her.

He's no longer faster, stronger, or swifter than a Slayer, but he's still a force to be reckoned with. Gunn and his crew alone had proved that a human could be a lethal weapon if wielded properly, and he's been doing just that since he was fit to hit the streets in hell. It's one of the many reasons why he's been able to keep this charade up for so long. He's just as dangerous alive as he is undead, thus making it harder for those around him to tell the difference.

That, and he's familiar with Faith's moves. That definitely comes in handy.