Webster's defines the word nerd as "an unstylish, unattractive or socially inept person; especially : one slavishly devoted to intellectual or academic pursuits. You may or may not be surprised that many managers and coaches in MLB fit that mold quite well.
There is a good chance that these guys were picked on during their primary years. Glasses, weird haircuts and all-around dorkiness are all good here.
Here is a list of the most nerdy looking managers and coaches in Major League Baseball.