I would think about selling him. I typically look for at least mediocre (preferably respectable or better) on the main defense for all of my players. I'm new at this, but I am shooting for an 11 or so man roster for the season - 3 trainees and a starter and back up for each other position.
You can often find players on the transfer list for cheap. I grabbed a 29 year old player with respectable OD, ID, Jump Shot, and Inside Shot for 11k a few seasons ago and he is still my back up SF. It might take a little bit of looking on the transfer list, but there are a few out there. For players that are not trainees, you don't need to worry about potential too; people often overpay for potential.