I know what Williams was talking about: Austin talked about it after the game.
Austin "stacked" the two defenders behind him by slowing down and "boxing" them out like a basketball player would on a rebound. Then, he bursted out quickly to grab the ball, effectively creating seperation by using his body. The DB was under the impression that this is OPI.
Unfortunately for him, since all Austin did was slow down (and he's entitled to his "space" in the field), that is not OPI according to the rules. Also, very hard to discern for the refs what's exactly happening.