In Major League Baseball, every team is supposed to have an ace. If your team is in a losing streak, he's the pitcher who gets your team back on the right track. In some ways, the ace's role is similar to a quarterback's in football.
The problem is, just like in football, not all aces are created equal. Some pitchers who are not equal to the task are put in that position for one reason or another.
For these rankings, I looked at the awards they have won, their won-loss record, how deep they pitch into games and if they have been consistent over a number of years.