I am not an expert in any way, so my suggestions are just a suggestion of what might work. Unfortunately, you might ruin and/or waste some leather in the learning process.
I am guessing a football will be sealed on the outside, so anything applied to the leather will have to be applied to the flesh side.
In the 1st attempt, I would wet the leather and place a heavy object on it, or clamp it between solid flat surfaces, (but do not use metal) while it dries. Maybe more or less water will be the difference.
If the water does not work, I would try a coating of some sort of leather lube, wax, lanolin or concoction of various ingredients. Different people have various leather treatments that the make and/or recommend.
Good luck with you research, I would be very interested to hear about your methods and results.