If we start Brooks play zone and let brooks run Billups all over the court on offense. Billups is good defender but at this point he is not quick enough for young speedy PG like Brooks. Remember Brook on the playoff vs Utah and all the problem Dwill have against his speed? As long as he don't get in foul trouble he will be ok. He can't be worst that Rafer the last game.
Brooks is a good change of pace, but on the defensive end, who will he guard? If matched up against Billups, he'll be posted up all night for an easy bucket or we'll have to double team which isn't exactly what you want to do to a PG.