the 28 year old is miles from his cap obviously, but i wouldnt play him at my training position unless he was there to win me games. He might go up a little from that over time.
the 25 year old is pretty close to as good as he's going to get, so if you are to train him his deficiencies are what you would prioritize assuming you anticipate keeping him.
the 23 year old is quite a ways away from cap, and is well behind in development.
If you have a 40k trainer that you just bought, i'd go buy a new player to develop. Otherwise, i'd be in search of someone cheaper than that. Thats on the expensive side of a level 5.