Hi, under the football pads the reflection doesn't work as good as worn as outside layer. nevertheless the sweat and temperature management do work as good as every other X-Bionic garment. Even better as the sweat is spreaded faster and on a wider surface. So you can wear it without any problem. My experience is that the fennec products a re more sensitive to strains. So take care and look how the pads influence the outside of the shirt. The manufacturer wrote somewhere that they are bringing a new version of the fennec thats more robust. I like the fennec a lot but I only wear it on the outside for biking and running. This works perfect. Under Football pads I would rather recommend the energizer shirts or if it is very hot the new energizer light shirts. The Combat Energizer should do as well very good, as it even has paddings to reduce the impacts of the football pads.