Could be, like in real life.."You'll never win anything with kids"
Seriously though, I think too young a team/player, means you don't have the experience (or maybe thats too deep for the game? lol), would be interesting to find two teams of comparable quality, but a wide gap in average age, and see the difference.
For me though, I wouldn't give up on him, I would try to build him some experience to go with that skill.
I have noticed, that the top performer in my league, is often some 30-33yo with a mid table team, so that maybe points to an "Experience factor".