ASHBURN, Va. — Five-time Pro Bowl left tackle Chris Samuels is out for the season with a torn right triceps, the latest blow for a Washington Redskins team that has sunk to last place in the NFC East.

Samuels was injured in Sunday night's 24-10 loss to the Baltimore Ravens.

Right tackle Jon Jansen was also hurt in the game and an MRI on Monday revealed a sprained MCL in his left knee. The Redskins said Jansen has not been ruled out for next week's game against the Bengals.

The dual injuries forced coach Jim Zorn to insert Justin Geisinger — a backup center who hasn't played tackle since college — into the game at tackle in the fourth quarter against the stifling Ravens pass rush. Geisinger struggled — and got hurt as well. He was having an MRI on Monday to address what Zorn called "a potential knee problem."

Zorn said second-year player Stephon Heyer will start the rest of the season at left tackle in place of Samuels, with journeyman Jason Fabini getting first shot at right tackle if Jansen is unable to play. At the very least, the Redskins plan to promote tackle Devin Clark from the practice squad and sign another offensive lineman to the practice squad.

Zorn shuffled his hands back and forth as he discussed the various permutations.

"We can't get any more injuries," Zorn said. "We just flat can't. They cannot get hurt. That's my mandate for them today."

The Redskins (7-6) have lost four of five and are in an offensive free-fall, scoring only 33 points in the four losses. They rank 29th in scoring.

Two defensive players also had injuries checked out Monday. An MRI on rookie safety Chris Horton's shoulder came back negative, and he is day to day. Defensive tackle Cornelius Griffin was suffering from an abdominal strain and was being examined for a possible hernia.

Samuels, who has been to three straight Pro Bowls, has been bothered by a sore knee for much of the season. The knee caused him to sit out the win over Detroit last month, the first game he has missed since 2003.