How long do you play for?
The rise you see without any insulin (I assume you have some basal insulin on board though!) is your liver being helpful and providing you with some glucose. Depending on how energetic you are (aerobic exercise produces less or no initial rise compared to a definite rise caused by anaerobic exercise) and how long you play for (there is only a finite amount of glycogen in the liver, though probably more than enough for a set or two of tennis I fear) you will get different effects.
I play badminton in the evening once a week, I take half my bolus for supper (and supper itself!) before I head out to play, I may initially head high, but I then tend to head low towards the end of an 1h30 session, so have a snack at that point. When I used to play during the day I'd probably have some residual bolus on board and would typically need to have a snack beforehand or during.
If you're playing 2h after eating, I'd be tempted to take your normal bolus for the meal (to avoid going high afterwards) then have a decent pre-game snack (20g+ uncovered) and some other odds and ends to eat as you play as needed.