(Assuming you are both righties)… It is likely they hit one of their backhands deeper in your add court and you gave them a shorter ball in reply, which they dropped shallow in your deuce court.
You charge in and get there in time to make a split-second decision on where to hit the ball. What do you do?
1) Hit a semi-aggressive forehand crosscourt,
2) Drop shot back over the net, or
3) Push the ball up the line
Most of us, me included, tend to try to drive the ball crosscourt; but that ends up in “losing geometry.” As soon as he hit the drop shot, your seasoned opponent immediately started coming in toward the net; so he sees you take your racquet back to go crosscourt.
He moves to the center of the court and all he has to do is get a racquet on the ball and block it back to the open court on your add side. You have just sprinted to the net to get to the drop shot; so it is unlikely you will be able to reverse directions and run back to the open court (unless you are young, Marc VanDam).
If you hit a drop shot in return, odds are your opponent will be there in plenty of time to again take control of the point with an aggressive drive or lob over your head.
If you watch the pros in this situation, their preferred shot is the push down the line. With your opponent coming forward, now they have to reverse course and try to get the ball back in their backhand corner.
And you have time to recover to get ready for what will likely be a weaker reply or lob for you to attack.
You can turn Losing Geometry into Winning Geometry.