What about Hewitt? What is his H2H?
Del Potro-Hewitt 2-1
overall top10-Hewitt 41-20
against the whole top-10 I don't think you will get interesting results other than Janowicz with 3 matches
but about lower ranked players (not guys like Hewitt or Davydenko with a great past) against one of the top-10, you can have interesting results maybe.