Thank you for your reply.
so that means the stamina will increase as regen grows older? but i also notice physical attribute is hardly for increasing than technical attribute. i.e there is an regen in my team with stamina 4 at his age 17, now he is age 20 and stamina is 5. only 1 point increase in 3 years even i have trained him in fitness training category.
I understand you may have algorithm for generating attributes for regen for matching some statistics data. Here is my guess, For the physical attributes, pace, stamina, stength. they are calculated in same algorithm. But players in different roles needs different stamina, i.e. dmf and wback needs more stamina from my perspective. so they cannot be calculated in the same way.