Rule 3.05

Rule 3.05

(a) The pitcher named in the batting order handed the umpire-in-chief, as provided in Rules 4.01 (a) and 4.01 (b), shall pitch to the first batter or any substitute batter until such batter is put out or reaches first base, unless the pitcher sustains injury or illness which, in the judgment of the umpire-in-chief, incapacitates him from pitching.

(b) If the pitcher is replaced, the substitute pitcher shall pitch to the batter then at bat, or any substitute batter, until such batter is put out or reaches first base, or until the offensive team is put out, unless the substitute pitcher sustains injury or illness which, in the umpire-in-chief’s judgment, incapacitates him for further play as a pitcher.
 
(c) If an improper substitution is made for the pitcher, the umpire shall direct the proper pitcher to return to the game until the provisions of this rule are fulfilled. If the improper pitcher is permitted to pitch, any play that results is legal. The improper pitcher becomes the proper pitcher as soon as he makes his first pitch to the batter, or as soon as any runner is put out.
 
Rule 3.05(c) Comment: If a manager attempts to remove a pitcher in violation of Rule 3.05 (c) the umpire shall notify the manager of the offending club that it cannot be done. If, by chance, the umpire-in-chief has, through oversight, announced the incoming improper pitcher, he should still correct the situation before the improper pitcher pitches. Once the improper pitcher delivers a pitch he becomes the proper pitcher.


DISCUSSION

The starting pitcher or substitute pitcher must
1.    Pitch to one batter (one at bat); or
2.    the third out is made; or
3.    the pitcher is injured, ill, or ejected. [J/R]


In 1976, California Angels manager Dick Williams inadvertently penciled Nolan Ryan's name as starting pitcher instead of pitcher Gary Ross. The error was discovered after the lineups had been exchanged and Ryan was required to face one batter, who grounded out.
http://mlb.mlb.com/news/article.jsp?ymd=20090518&content_id=4798510&vkey=news_mlb&fext=.jsp&c_id=mlb&target=Z&source=PJ_AD:Z:MLB&affiliateId=21181&clickId=405371104&affiliateCustomId=skim725X143400X00d3488580b7257ea1fc0ebb33da98cb

The visiting pitcher cannot be pinch hit for until after he faces one batter.

Pitcher is injured before throwing pitch and is replaced.
http://mlb.mlb.com/video/play.jsp?content_id=5693291

Larry Yount

Larry Yount, Robin’s older brother, injured his arm in warm ups before his first, and only opportunity to pitch in a big league game.

Manager pulls substitute pitcher claiming injury
http://mlb.mlb.com/news/article.jsp?ymd=20110621&content_id=20801764&vkey=news_tb&c_id=tb
And video:
http://www.usatoday.com/sports/baseball/al/rays/2011-06-21-Joe-Maddon-MLB_n.htm