Player's progress in this game:
18-21 = 1/1 progress
22-25 = 1/2 of own progress at age 18-21
26-29 = 1/4 of own progress at age 18-21
30+ = 1/8 of own progress at age 18-21
And, if you ask me, this is one of the most stupid things in the game... The last day of a season, at age 21 it's full progress and the next day, at age 22 it's 50% progress... This gap should be 25% at max... Training of 26+ old players is literally waste of time or resources, because their seasonal progress is 5-6% or 2-3% for players at age 30+...