Sahni is a very good guard trainee. I like him a lot. He would be well worth focusing on if you decide to train guards.
Without seeing his skills, Tannui Lee might also be a good trainee at C. His age, height, salary, and potential all look fine.
Other than those two guys, I don't see anyone else on your roster that is a great candidate for long term training. I recommend deciding on training bigs or guards, selling off either Sahni or Lee (whichever one you won't be training), and then adding a bunch of new trainees.
The draft is coming up in a few weeks, and you may want to wait until then to decide on your long term plans. Looking at your current roster, I recommend training guards (at least for the short term).
If you'd like some more help with anything, feel free to send me a BB-Mail.