I firmly believe that every major professional sports league is willing to twist some knobs and push some buttons in order to ensure/avoid certain outcomes which might be extremely beneficial/damaging to their business. Something as simple as fixing a draft lottery in advance, even just for the top player to be drafted, can have a huge impact on growing or shrinking certain teams' fanbases/markets. You could probably accomplish it with only a few people aware -- wouldn't need the entire league to be in cahoots -- and it's not really something like matchfixing.

And I'm sure that referees in most leagues are given directives about which players to favor, etc. In hockey, at least, it's really apparent that the superstars tend to get treated with kid gloves by the refs.

Having said that, I firmly do not believe what some others do, that entire sports are rigged a la pro wrestling. I think the leagues will, on rare occasion, step in to protect their investments. But I don't think someone's sitting behind the scenes writing out the storylines in advance.