Earlier this week, Leftwich said he was ready to start after sitting out the last two games because of a knee injury.
"He was able to work in full pads and moved around pretty well," Del Rio said after an afternoon workout.
Twelve-year veteran Jason Garrett, 38, signed with the Miami Dolphins for the remainder of the season, one day after backup quarterback Jay Fiedler was put on injured reserve because of a herniated disk in his neck.
Garrett will be the No. 3 quarterback behind starter A.J. Feeley and backup Sage Rosenfels.
Linebacker Mike Barrow, who hasn't played this season because of acute knee tendinitis, was put on injured reserve by the Washington Redskins.... Tampa Bay put defensive tackle Anthony McFarland on injured reserve because of a torn triceps that required season-ending surgery Friday.... The Redskins said they were not participating in an NFL experiment in on-field seating against the New York Giants on Dec. 5, as announced by the league Tuesday.... The San Diego Chargers will raise prices next year by $8 per game for season-ticket holders and $12 for single-game tickets.