Smith sprained his right knee in a win at Oakland two weeks ago and came out after one series in last week's loss to Seattle, which eliminated the Cowboys from playoff contention. Scandrick sustained small bone fractures in his back against Washington and missed three games.
Dallas filled the open roster spots Friday by promoting offensive tackle Kadeem Edwards and receiver Lance Lenoir from the practice squad.
It was a difficult season with injuries for Smith, who made his fifth straight Pro Bowl. He missed two games and sat out practice frequently while dealing with back, hip and groin issues.
After missing just one game in his first five years, Smith has been out all or most of seven games the past two years.
More AP NFL: http://pro32.ap.org and http://twitter.com/AP-NFL