Defensive coordinator Greg Blache also says Thursday there will be strategic changes when Washington (1-2) hosts the Tampa Bay Buccaneers (0-3) this weekend, with a more "maverick" approach.
The Redskins' defense ranks last in the NFL in third-down conversions, allowing opponents to convert 51 percent of the time.
Doughty, a fourth-year player, hasn't started a game since Oct. 5, 2008; he missed most of last season with a back injury.
Horton replaced Doughty in the lineup and started 10 games in 2008 as a rookie. Horton also started the first three games this season, although Doughty did get playing time, too.