Pitchers can be a funny lot as you don't know what they are going to do from one start to another. One outing they can look like Cy Young and the next a little leaguer. I have had pitchers that should be Cy Young candidates with their ratings but the offense never produces. Never figured that one out and was always frustrated with the 2-1 wins or losses then the next day put up 10 or more runs. I have had an emergency pitcher with bad ratings generate a 16 win season, never figured that one out either.
Starting pitchers are usually defined by being able to get to the seventh inning at least for the most part anyway. They need a stamina of 70 or more and a durability rating of at least 25 to pitch in a normal rotation. Over 60 but under 70 will get you through the fifth if they are good but can tax the bull pen. To explain more fully, the stamina rating is the number of pitches a pitcher can throw before becoming fatigued then add on another 15 before he really needs to come out. The durability rating for a pitcher is his recovery time from fatigue after pitching, normally a one for one item. Most games takes approximately 120 to 140 pitches to complete.
Long Relievers are usually the ones that have the 55 to 65 stamina and can give you 2 to 3 quality innings. I like to call them middle relievers myself as an overall general term, most generally unsung heros. I don't set my rotation with long relievers myself as I use them all as Setup A. Lot of times you will have an extra stater on the staff in the pen which is a widely excepted idea.
Setup B relievers normally have low pitch counts with a high durability and are used to get out of an inning or pitch one inning before the Closer comes in. No more than two on a roster normally.
A Closers job is to finish the game off for the win. They also have a low stamina and high durability and normally the cream of the crop.
There are also some specialist settings you will find though the game doesn't use them correctly if at all. The game likes the Mop Up position but I rarely use it unless I have to call up a pitcher and I don't want him in if the game is on the line.
Now for the nuts and bolts. Control, splits, and pitches need to be as high as possible. Hard to come by and cost lots of money. I myself like high control, 80's or better. Splits can be a little give and take. Lefties generally have a lower right split but that doesn't make them a bad pitcher as many don't like them as there are more power right handed hitters. Most generally the right split needs to be in the 70's or better, lefties in the 60's. I have actually had better luck with lefties in the high 50's which is common. Lefties with a right split in the 70's or higher is uncommon but do exist. I like the first two pitches to be high, upper 80's and 70's with pitch 3 and 4 in the 50's and 60's.
To go with that is FB/GB, GB is the high end of the spectrum while FB is the low end. Does it really matter? Most say not really, me, well I like the GB as power hitters aren't going to put it over the fence as much. Last but not least is Velo, Most like it high as these are the high strike out pitchers. I wouldn't have a stable of just FB pitchers nor would I have a staff of low Velo pitchers either.