Not sure exactly but from my experience and what others have posted its gonna go on a teams needs and the coaches prestige. So for example if someone has an A+ prestige, they may be offered 20 or so different positions (just made that number up for an example) and if the coach you mentioned has a much lower prestige, he may only be offered 1-2 if any at all. Also keep in mind that a position needs to be opened to be offered. After my first year of OD I had a C+ prestige level and was offered 3 positions (OC) and that was it.
Im not sure what happens if your contract expires and you dont get offered a position. If any have had this happen it would be cool to hear about it.