Ganther moves ahead of Rock Cartwright, who started the last two games.
Clinton Portis started the first eight games before suffering a season-ending concussion. Ladell Betts took over for two games before his season ended with torn knee ligaments.
Cartwright rushed for just 77 yards on 28 carries in his two starts.
"I'm a little disappointed, but what can I do about it?" Cartwright said. "I'm not going to lose no sleep over it. I've still got a job."
Ganther has been signed, released and re-signed by the Redskins during this season. The second-year back from Utah ran 13 times for 78 yards -- a 6-yard average -- while backing up Cartwright the last two games.
"I'm getting the opportunity that I haven't had to show people what I can do," Ganther said. "I just worked harder than anybody. The longer you keep you feet in the door, the better opportunity you have."
Copyright 2009 by The Associated Press