ASHBURN, Va. -- The rumors swirled about, as they often do in Washington. Mike Shanahan was benching Robert Griffin III to force his own ouster. He was doing it as a parting shot to an organization he wants to leave at season's end. Or to upset a player with whom he does not get along.

Shanahan said the move had nothing to do with any of that. Rather, he said Griffin has been hit too much in recent games and the coach wanted to make sure that the quarterback reaches the offseason healthy -- something he did not do last season because of torn ligaments in his knee, missed time that cost him a chance for more success this season.

Therefore, Shanahan said Kirk Cousins will start Sunday against the Falcons in Atlanta, and Griffin will not play again the rest of the season. Rex Grossman will be the backup. All of this comes amid the backdrop of Shanahan's uncertain job security, with his return for a fifth season in serious jeopardy. He said all of that is not relevant to Wednesday's decision.

"The best thing to do is give him an opportunity to go into that third year injury free to get a chance to get better in the offseason," Shanahan said. "I know that will be the difference in him being 100 percent healthy and him going to the offseason being the leader. I think it would set him back so much if he missed another offseason, which could happen. I didn't think the risk-reward was worth it.

"When you take a look at a quarterback who is your franchise quarterback, he's your future. If you miss two offseasons in a row it'd be the hardest thing to recover from."

Griffin was dispirited during his nine-minute news conference, looking as down as he had all season. During the portion of practice open to the media, he stood in the background, holding his helmet behind his waist, and watched Cousins and Grossman take snaps with the starters and second unit, respectively.

Griffin said he lobbied Shanahan to remain in the lineup, something the coach expected.

"Coach's decision is what we go with," Griffin said. "That's the way it's always been, so I have to do that. I have to sit here and do whatever I can to help Kirk, do whatever I can to help this team win. In times like these you just have to lean on what you've been taught in life and my parents, being military parents, have taught me to respect authority, and I have to respect what Coach says."