Many things are imported randomly and are not historically accurate. Much research and editing are required if you want realistic ratings.
Also keep in mind OOTPB does not totally recreate historical leagues...some great players will only develop into average, fair or mediocre players...while some average, fair and poor players might develop into great players. But overall will play as in real life.
This is a very good thread on the subject.
http://www.ootpdevelopments.com/boar...+range+ratings