He's starting to notice how much stronger Nick is, and he's worried that'll be a problem in close quarters. That can turn into a wrestling match in a hurry, and he usually loses those.

His best defense is to just be faster and wilier, so this time when Nick comes at him he makes like he's going to block, then just drops at the last second to tangle up Nick's legs. If they weren't both fast healers, the vampire would have bruised shins by the time this is over.