The thing is though that every match (major leagues and cups) is covered by 100+ books most of which have a big range of handicap and alternative markets. If you look hard enough there are nearly always highly correlated plays available that have +EV (or arbs, of course) if you look hard enough.
Sooner or later, of course, the gravy train grinds to a halt when the books limit/boot you but that doesn't mean you shouldn't ride it while you can.