The highly paid defensive lineman has yet to play or practice regularly with the starters, but he is slated to see work in nickel packages and passing situations, the source said.
The news comes one day after Redskins tight end Chris Cooley told a Washington-area radio station that in addition to practicing with the team's nickel packages, Haynesworth had been working with the scout team this week.
On Tuesday, two people with knowledge of the negotiations told The Associated Press that the Redskins were talking to the Tennessee Titans about trading Haynesworth, who has been a nonstop headache for coach Mike Shanahan during his first eight months in Washington.
Shanahan brushed aside the rumors, saying Haynesworth would be ready to go against the Cowboys.
The Associated Press contributed to this report.