older players training faster than younger players?

I don't get it. I was told that younger players will train faster than older players but I have a 18 yr old 4 star player that gets only half of a 24 yr old player (3 star)

the 18 yr old player usually gets one of the lowers gains when it comes to training.

why is that so

I think the young fella isn't a fast trainer & the older fella was

You need to look at His age and at His market value.
The highest the market value, the faster he will train.

so the only way to know whether the player is a fast player is through the market value? dang i thought i had a good deal when i bought him