Major sports leagues are not rigged in the sense that winners are pre-determined, but the refs are told to keep games, serieses, and playoff races close, because blowouts and dominance are boring.

An NBA ref got busted for betting on games and IIRC talked about how the league would make the above obvious to refs (at least in the postseason). There's too much money changing hands and too little accountability for shady shit to not happen at all, and this is the type of thing all owners could have a handshake agreement on because they'll all profit from it and it doesn't really prejudice any team specifically.