ASHBURN, Va. -- A Washington Redskins team that opened training camp with veterans Clinton Portis, Larry Johnson and Willie Parker in the backfield will likely go into the Minnesota game with a trio of Keiland Williams, James Davis and Andre Brown.

Coach Mike Shanahan announced that Portis has a torn muscle in the lower abdomen and is done for the year. Portis managed only five carries after returning from a torn left groin that had cost him five games.

Ryan Torain, who claimed the starting job when Portis first got hurt, is expected to miss his second straight game with a hamstring injury. That leaves Williams to start, with Davis -- who was promoted from the practice squad Monday -- as the primary backup. Next up would be Brown, a 2009 New York Giants draft pick who has bounced around with four teams and will be signed by the Redskins once he passes a physical.

Safety LaRon Landry isn't expected to play against the Vikings, either, but Shanahan acknowledged Wednesday a concern that the team's best defensive player over the first half of the season might not play again this year at all. Landry's left Achilles tendon is inflamed, and he can't run because of the pain.

"We really have no choice but to rest him." Shanahan said. "If you play through that pain, there's a chance of rupturing the Achilles, and we don't want to do that."

The news was more vague about the other injured players. Shanahan said he'll have a better idea about offensive linemen Casey Rabach (knee), Artis Hicks (thigh, groin) and Derrick Dockery (knee) and linebackers Rocky McIntosh (groin) and Lorenzo Alexander (hamstring) during Thursday's full-speed practice. With the offensive line situation so dicey, the team added Jacob Bender to the practice squad. Bender's NFL career consists of two games with the New York Jets in 2007.

"Any time you're down as many players as we're down, if you had a normal practice you wouldn't be able to function on game day," Shanahan said. "We had 15, 16 guys that cannot practice, and you can't hold a normal practice. Every once in a while you have these situations, and my experience is to give them as many reps with the game plan [as possible] but don't overdo it."

Cornerback Carlos Rogers said his ailing right hamstring is doing better, but he hasn't tested it fully. Rogers, who didn't play Sunday, said the nature of hamstring injuries makes it difficult to guess when he'll return.

"The hamstring," he said, "has a mind of its own."

Landry's injury left the Redskins with only two healthy safeties, so another new name is Macho Harris, who was signed on Tuesday and made his practice debut Wednesday. Midseason pickups usually get a week or two to learn the system before they're asked to play, but Harris will almost certainly be active for the Vikings game.

Harris went to high school locally and played in college at Virginia Tech. He played last season with the Philadelphia Eagles but was cut at the end of this year's preseason. To pass the time, he's been playing in a flag football league to stay in shape and hone his technique, but he tried not to let on that he was an NFL player out of work.

"I tried to stay under the wraps. I tried to put on extra clothes and tried not to be seen because I didn't want it to be anything crazy," Harris said. "But it was fun."

Information from The Associated Press contributed to this report.