Numpty >>
tuesday march 24 - 14:11, Edited
tuesday march 24 - 14:15 I think that's a question that only you can answer.
It depends entirely on your future plans and how you intend to develop the club. He's currently one of your better players but is unlikely to remain so if you make good progress over the next few seasons. So by the time he's in his mid 20s he'll probably just be a squad player and not a legend. You just don't have the training facilities to get the best out of him.
If it were me I would sell him. I would use the money either to spend on construction, or buy better - older - players, or reinvest in the transfer market to make a profit.
I have a similar struggle with some of the youngsters that I've had for 4-5 seasons. I start to feel a bit sentimental about them and keep them a little bit too long when I would be better selling and taking the cash. This frees up the squad space that can then be used to make a better profit.