Walcott faces more than three months on the sidelines after sustaining the injury in training.
"There have been some agreements and the overall issue is about how the players can be paid by the club and play for somebody else. That is a basic way of thinking.
"That is why sometimes it happens that you do not see the player for three months and the clubs pay them. You have to find a reasonable agreement.
"It can only be regulated by FIFA because the difference of wages means it would be too big for some national federations."