It's not hard to draw an analogy between the situation being described by FIFA and Noel Gallagher's comment that,
'I was trying to get off drugs, but I only swapped illegal drugs for prescription drugs. If you’re on private health care, they’re only too willing to dish them out. Ask Keith Richards.’(MK note - I don't have a clue what happened to the font there; this is like blogging in large print. Maybe Derek Jacobi might be available for the audiobook version).
Obviously the major factor in such matters is the health and well-being of the players; however if the painkillers being abused in football are solely off the shelf medicines that the players have provided for themselves, then FIFA needs to beef up the doping laws. However if the players are being prescribed or given such medications by the doctors provided for them either by their clubs or by their associations, FIFA needs to get creative, and determine whether the provision of these medicines is providing teams with an unfair advantage. If you have too many players on painkillers, you are not fielding your strongest possible team but one which is even stronger than the strongest you could field were all players to be available for selection in their natural and immediate states of health.