I am assuming it is Kirby you want to train. You have to play him 48 minutes per week. So far he hasn't played at all. So in your next game set him as the backup to your regular center and in your scrimmage (very important to schedula a scrimmage every week for training minutes) list him as the starter. Then on the training page choose something that trains centers (inside shot, for example) and on Friday you will hopefully see him start to improve. I would be training Sams and Kirby at one position training, making sure that both of them play at least 48 minutes per week at center.
Once I scored a basket that still makes me laugh.