Observation

[aeasao]

You are right that with age players training gain slows down. Especially the jump from 21 to 22 years makes a big difference. The star quality of a players also makes a difference. For eksampel, a 5* player in level 1 is 24 quality. In level 2 he is still 24 quality, but now he gains training points as a 4* players. I believe this is what you experience.

Unassigned skillpoints also affects the star-rating and quality of a player. So if you have a player that is close to the next star, it could be a good idea to invest all the training points in a special ability or new position as soon as you get them. I have a player that had unassigned skill points, and his training gain decreased, once I invested them in a special ability he regained his previous training speed.

When Stavrakakis was a 4* player with unassigned skill points (making him a 5* player in the eyes of the code) he gained around 25%, 60%, 85% when I trained him on three bars (that is high intensive training = power training). When I assign the skill points to special ability, making him a 4* player again, he regained a training speed like 35%, 75%, 120%. Quite a difference!