Something we've been practicing lately...
Defensive responses are required at different times during a fight, whether it's sparring or "for real".
If you've got lots of time, and are at long ranges, you can do all sorts of things. Some of them are pretty fancy, some are fairly simple. But the common trend at that point is that you have all sorts of time. Maybe you just plain leave; maybe you do some sort of evasion and counter attack. Maybe you just punch the other guy in the face while he's trying to cover the ground to hit you...
More typically, we fight at middle ranges. Not quite able to hit the other guy unless you take a step or otherwise close the gap. At that range, we've still got a lot of options. It's the heart of where our club trains. As soon as they move, we move and counter. There's time here to block & counter, using patterns we practice.
Sometimes, we miss the signs. Maybe we've let the other guy steal a bit of distance. Maybe we've just missed it. But we suddenly see the attack, and we still have a moment to respond before we get hit. That's where our emergency techniques come in. We pull back and kick, or cover and strike. But we've still got that beat of time before we take damage.
And sometimes -- we're taking damage before we know something has happened. We've practiced a drop-step technique. The idea there is simple: damage is happening, we don't have time or maybe even faculties to do an evasion and counter-attack. So, we cover as best we can, simultaneously strike-blocking, aiming to disrupt that attack and buy some space and time to recollect and shape a better response.