Comicwoman: I would want the senior pilots to do the trans-oceanic (at at least trans- Pacific) flying. There was another WSJ article posted some weeks ago about an UA near crash (oxymoronic since a plane either crashes or does not crash? Need help with English here, Mr. Merry!) because most pilots lack the experiences in flying 747s, the plane most used for trans-Pacific routes.

I think in this case, the pilot is making more of a statement rather than actually physically tired. Four people flying a route that is on auto-pilot most of the time does not seem too taxing, IMHO.