Hurricane Sandy caused the postponement of tonight’s Nets’ opener (but not tomorrow’s Knicks home opener, Sunday’s Giants game, or somewhat controversially, Sunday’s marathon). Now it’s also forced a change in the MLS playoff schedule: The Red Bulls — who play their games in Harrison, New Jersey, near the Passaic River — are set to play D.C. United in the conference semis. It’s a two-game, home-and-home series, which will be determined by total goals. But Red Bull Arena, which was mostly undamaged, has no power. (It has generators, but it could be days until normal power is restored.) D.C. United, the better seed, was supposed to visit the Red Bulls Saturday and host them next week, but because of the circumstances, they’ve ceded their home-field advantage, and instead will host the Red Bulls at RFK Stadium on Saturday night, then visit Red Bull Arena on Wednesday. United fans – or at least, some vocal ones on Twitter – don’t approve.