played (just a single game?) but not contracted right? Does playing one game eliminate him from a chance of a rookie contract?
I don't think that is in the public domain but I'd like to know the answer too; always have.
There's not a lot of significance in the rookie category except that (so some journos say) every Super outfit has to have so many rookies on the books every year. This means that in year 2 they have to be promoted to a full contract (unless, as in the case of Peterson, it's part of a 2 year deal already) - or be dropped from the squad.
The other side of that is that if the rookie is contracted for year 2 then a full contract guy has to be let go to make room for him. This enforces rotation in the squad and the rise of youngsters. In 2013 Peterson will, in effect, take the contract spot of a Tah player whose contract terminates at the end of 2012.
Josh Holmes told me a few years back that rookies have to do extra technical work for their position above and beyond what the others did and that they were on the base salary.
The old requirement was that Super squads had to have at least 3 and not more than 5 rookies in their squads every year.