User blog comment:Staw-Hat Luffy/The Shichibukai That Fought Z/@comment-972068-20130426140303

If you remember that time the Marines were discussing about Doflamingo's leave (it was when Buggy was confirmed), he listed all of the 6 current and "the one I mentioned earlier" making 7. The Warlord that cut off Zephyr's arm is most likely this one we never heard about, so we still don't know who it is.

As for their appearance making Film Z or Zephyr canon, that may not actually be true. Oda could have used Film Z as a non-canon plot device to foreshadow it all. If the Warlord actually talked about the events of Film Z, or stated that he cut off his arm in the manga, then that makes it canon. Otherwise, it's just clever foreshadowing.