Stamina is required for long innings, but does nothing but help a reliever. Each pitch thrown takes off some of their 'energy' Stamina is how MUCH energy is used, and how MUCH is recovered between pitches/innings.
I agree with the above for the most part....if a pitcher doesn't have at least 3 pitches, preferrably 4...they should be in the pen in most cases.
Any player under 7-8 stamina should NOT be in the rotation, unless your bullpen is very, very deep.
Cory