market gaps down like yesterday when they need more shorts to fuel the rally.. the juice market up into close so shorts get margin-called out at higher price. Then take the futs down into market open so shorts can add back their positions at a lower price then be used as rocket fuel for rally.....this way "they" don't have to use as much Fed repo money to juice the market.... (see yesterday gap down as example) Fed OMO http://www.newyorkfed.org/markets/omo/dmm/temp.cfm