Xander can defend himself and others pretty well with his fists or a stake, after years working beside Slayers. He's got no formal training beyond whatever he still remembers from his much-faded soldier-memories from a spell about ten years ago, but on the other hand he's got ten years of informal but frequent experience at it.

He's also handicapped by lack of peripheral vision on his left side, and problems judging depth/distance with stuff that's tossed at him or moving towards/away at close-quarters. As a random example, if he dropped a stake and needed to grab it from the ground again quickly, he might be in trouble, and when throwing a punch, he might hit either too hard, or not hard enough if whatever he's aiming for is further away than he thinks it is.