At the end of the season they are determined by head-to-head but at this point since teams have only played each others once it's goal difference. So Milan are at top but it doesn't mean much.
I know Pepe works hard and all that but starting him in the center behind a striker instead of someone like Del Piero or Quag was disgraceful. If you can't play him at the wing don't play him at all, period.