Starting Pitcher Return to the mound

Question
Under the MLB rules, can a starting pitcher ever return to the mound for any reason?  I have been told that the starting pitcher can leave the mound in a defensive position and then return to the mound.  I have also been told that Fernando Valenzuela used to do this with the Dodgers.  Any information about pitchers returning to the mound would be greatly appreciated.  If there is a rule number that is associated to this discussion please let me know.

Answer
David,

There is no rule prohibiting a pitcher from moving to a different position then returning to the mound.  As long as they stay in the game, they can play whereever they want.  When a player is removed from a game, they cannot reenter for any reason.

I'm not sure about Fernando, but I know that Whitey Herzog used to use Cardinal pitchers in the outfield for a batter, then let them go back to the mound, in order to get a platoon advantage.  For example, he would move right handed Todd Worrell to right field and bring in a left hander to face one left handed batter.  Then, after the batter, Worrell would go back to pitching and a new right fielder would be brought in to replace the left handed pitcher.

Hope this helps!

Brian