Talking, reacting to the poach right at you, right?
YOU, knowing that anything weak will be put away, needs to think beforehand, "don't volley right back". You have to know the hole you're going at, or the lob volley you're gonna try. The hole is a winner, between the two opponent's or down an alley. The lob volley is also a winner attempt, as anything less will be crushed down your throat.
You know what you should be doing because that scenario has happenned to you many many times before. Your partner puts up a weak groundie or volley, you are in position to EAT the ball. So you preplan what you're gonna do when opponent poaches and hits within your racket's reach.
Now if the poacher is strong, can volley with pace, just turn around and give up the point. But you have reactions. If the poach is a normal volley nto your chest, you have plenty of time to reflex lob volley into the open court, then move forwards to center of service box. That lob volley is purely offensive.