Mack worked with the Brown's first team during Friday's practice after standing to the side and observing earlier in the week. He later boarded the Browns' team flight for Oakland in another positive sign for his status.
Mack, who had surgery on Oct. 3, said he's been feeling better every day and it will be a game-time decision whether he faces the Raiders. Mack has not missed an NFL game in three seasons.
Browns cornerback Joe Haden did not practice again because of a sprained left knee. It's unlikely the Browns (2-2) will have their top defensive back on Sunday. Coach Pat Shurmur said Haden has been getting treatment all week. Haden has not been in the locker room during the periods it has been open to the media.
If Haden doesn't play, Dimitri Patterson will start in his place. Patterson made 10 starts for Philadelphia last season.
The Associated Press contributed to this report.