I don't believe sports are rigged. At least, for the most part (outside of wrestling).
Here's my reasoning:
1) You can pay-off refs and umpires to call games to favore one side.
2) you can throw a game by intentionally not making a play or multiple plays.
3) You CAN'T count on a player to make a spectacular clutch catch, shot, or hit.
There is too much of a margin for error. You drastically increase a teams chance of winning. But you also have to do it without making it seem so? I just can't imagine it would be possible without having become general knowledge by now.