On the MLB Gameday thread they always call Flaherty Flats (or MFF; take a guess) or Lawn King (because some say Buck keeps him around because he mows Buck's lawn),
Brach is Bad Brad, O'Day is sometimes called D-Day, Wieters is usually referred to as Wiets. Ubaldo is Jimmy Nez. A lot of players are referred to by their initials. AJ, CD, CJ, JR, etc.)
Interesting factoid about Flats: His Wiki entry once said "He is unarguably the greatest American born baseball player in the history of Earth." If you click on his 'view history' tab (in the upper right) & go to July 23, 2014 it's listed there.