Personally, I don't train my mindset for blocking any strike coming in slow enough to see, ie: blocking based on an aggressor's attack. Even in sparring I reflexively transform into a full body block that is an obstacle instead of the body image my attacker struck out at. (modified crane). This gives me a moment to assess the status of the attack. Friend, foe, (intent), weapons, alone? The faster the ability of the opponent, the less likely you will see what you are being struck with. Like to fight unarmed as I would while holding a sword or short staff. Also, I won't attack an opponent on the grounds of what I see but by what I have prepared for him/them.