Oakland coach Lane Kiffin made the announcement after the first of two scheduled practices Wednesday. Andrew Walter, who started eight games for the Raiders a year ago, will be McCown's backup while veteran Daunte Culpepper -- signed earlier this week -- will also play.
"The three of them will play evenly, for the most part," Kiffin said. "We'll try as best we can. Sometimes the reps won't be exactly even … but for the most part they will play evenly."
Kiffin reached his decision earlier in the week but held off making an announcement until he had a chance to speak to the quarterbacks.
Further muddying things is that No. 1 overall draft pick JaMarcus Russell is unsigned and not in camp. Four days before the game against Arizona, Kiffin indicated the two sides were not close to reaching an agreement.
"At this point it's going to be hard for JaMarcus to be ready to be effective for this team," McCown said. "So for us, my mindset, you don't really kind of worry about,. ‘Are you going to lose your job?' I'm focusing on being the starter on this team and help leading this team in the right direction.