It's not exactly a contact sport.
They'll just introduce a new rule that players have to keep 2m away from each other. It will be enforced by wearing GPS bracelets that will give electric shocks when they get too close.
Or players will be sequestered like for Big Brother, after quarantine and tests, and will only come out to play.
It should work.
More seriously, in a future "normal" life with more tests and protective gear in most close situations, the risk from playing football should be low(ish).