With the season winding down it is time to do an in-depth study of your team. For many this would be an approach to determine needs for next year and I use several steps to quantify those needs. Also advancement of minor league players and possible changes to their position assignments as this item gets cut off sometime during playoffs.
One of the big things to check first is FA and Arbitration eligible players. Maybe not so much with the minors, but one must be aware of the those also. Is the FA player worth signing long term now, or is age and decline an issue to hold off till the start of next season, in either case I wouldn't release them because they might bring in an extra pick or two in next years draft. The arbitration guys that I don't want, I tend to wait until the second round of the playoffs before releasing so I don't forget to do it before the next season. Either way you know which player(s) that replacements are needed either by promotion or next years FA market. Sure helps to know now before crunching next years budget.
Player performance on the field is a big issue for me. I start with defense first, I look at their play on the field in errors and plus/minus plays. From that I examine their ratings as to whether they are playing the right position or a better position might be a better fit. This applies to players that have a long way to go to meet their projections. Playing them lets say at SS and is young and projections will take 2 or 3 years to get close for the position, you might want to play him at a position he can currently play. I have noticed by doing this they tend to advance more rapidly, like playing the SS at 3B will improve the glove and arm faster than letting him commit error after error at SS, especially the ones with makeup and patience problems. But don't forget to play him some at SS during the season also along with other capable positions. Doing this entails changing his primary position and leaving the others as a backup position. Also another thing to note is left handed players are frowned upon in the infield except 1B. So that left-handed infielder could be better served playing the outfield as a primary position.
Plate performance is also a big driving factor though not as much as defense IMHO. A good hitting player is almost useless in the lineup if he can't play a good defensive position. He might win you 10 games with his bat, but will lose you 10 games with his glove. Is that actually a good trade off? A better defensive player and lesser hitter may get you 5 wins with his bat but not lose 10 games with his glove. I'll take the extra 5 wins myself. Think I will call this the Hartman effect...lol Remember the C/DH I was trying to get rid of at the start of the season? He has 30+ HR's and 100+ RBI's this season at DH, but my pitching staff is better off without him behind the plate as the backup that doesn't hit well has done a much better job as I have the best CS% in the AL and 0 passed balls. You might say that has only given me 8 wins over last year with 7 games to go, but one must realize I have been resting players heavily since roster expansion opting to play callups. Could call it the Thompson effect also, remeber the FOY from season 1 that had a disasterous season 2? He is back to season 1 performance and I think the catchers was the key.
Pitching is the toughest to evaluate. I have heard this, that and the other thing of what makes a good pitcher. To me it is more trial and error as to what works for you and your team. Some say if the pitcher doesn't have 80+ control to start with, he has no businees in the ML. I can see their point on this, but getting at least 12 of these types is not the easiest thing. I have a world that has 12 of these types and good splits and pitches also, it isn't working. If you have a pitcher that has an ERA of 4.50 or less and a OAV less than 2.75 he is worth having IMO. Of course you have to be carefull using just those numbers as catchers and defense inflate or deflate these numbers more than you think.
As with any player, they can have a bad season including pitchers for no reason at all. Something I have noticed though, if a players ratings and stats don't correspond to their play or they seem to stop playing as expected all of a sudden and fatigue is not an issue, then they could be playing injured. Try resting them for 3 or 4 games and see if that helps. If it is an injury and you continue to play him, it will more than likely be a big one. Pitchers are harder to spot in this regard, but if two games in a row he only goes 5 innings or less with a high pitch count from the norm then he is a candidate. Like I said, hard to spot, as who remembers their previous game? But if it looks out of the norm for him, go back and look at the previous two games. Two in a row should look suspicious and I would skip him in the rotation once. Then again, I could be all wet about this.
One other thing I have noticed in the minors. Most players get 5 ratings boosts during the season. If your at the end of the season, like now, and they only have 4 they are begging for a promotion so it seems. They had a thing in the forum about this, some play it off as bad coaching or not getting enough playing time. I am not sure about this myself, most of the time if you promote him he will get the 5th boost though. Rookies only get 2 and maybe another from a promotion. But why promote a player you really don't want to promote? He may retire next season for one, so watch the ones you really want to keep in this regard.
The last thing I look at is health. I usually don't keep players with bad health, below 60. I will keep them if they are good and take a chance. However, if I have a log jam at the position, they are the first to go regardless.