although as bowlerdude and kflash89 will tell you I am by no means the expert

I got a player a few weeks ago and i still don't know where to use him...

Here are his stats, I bolded the good ones

Positioning..2....Tackling...2.....Punting....3
Vision..........7....Blocking..4.....Speed.....13
Intelligence.7.....Passing...7.....Strength..15
Footwork.....1....Catching..3.....Agility......7
Carrying......7....Kicking....1.....Stamina....6

Teamwork....19
Consistency..20
Age 16

His natural position is Kick returner


what would you guys do with him?
Not for sale of course

For me, I'd put that 21 year-old as a linebacker. The reason I say this is because if you say you have reasonable QB's who are in their 30's, then you likely have about 40 training periods before you need a new QB (20 weeks/season, at least 2 seasons before they retire if they're not retiring this year). This guy DOES have a pretty good Intelligence rating, which is important because you can't train it, but it's also supposedly very important to LB's (according to merc).

Given that it's such a long time that he has to train before he would have to play at QB, he would of course be able to train his passing rating, but even at 40 training periods, you won't be able to get him much above a 7 or 8 passer rating (even with focused training and high TW) by the time he has to start in season 4, and he won't get much work on his other skills, and by that time, the better QB's will probably have much higher ratings than this (for example, by the beginning of season 4, I expect my 23 year old QB with a similar TW to have a passer skill of at least 10). This is especially important, because in my experience, the difference between a good and bad QB in GI is much more significant on the field than the difference between a good and bad anything else.

Alternatively, in the same 2 seasons, you could train the guy at LB and leave him on "all skills" and not lose those extra training points by having to focus on certain skills, and he will likely develop into a much more well-rounded player. He will also probably be able to help your team sooner as a LB than he will as a QB.

In summation, I would personally train him as an LB, try and strengthen the rest of your team, build your stadium, and try your darndest to buy a player in 5 or 6 weeks with at least 5 passing, 14 int, and 15 TW. For example, this guy [playerid=]4772 is currently on the transfer list for 13000, though he will surely go higher, or this guy [playerid=]138251 with pass 6 int 17 TW 20, although his price will also surely rocket, or even this guy, who's slightly lower TW might allow you to get him cheap [playerid=]182481. In the meantime, try and trim the fat (like whatever LB you would've had starting, and that 18 year old that you just drafted), and save 3000 a week!
If you decide to keep this guy at QB, then definitely get him the start whenever you play a bot team, or a friendly, as he'll need all the rating and experience he can get with his lower passer rating.