Randy Thomas is out for the season after suffering a right triceps injury in Sunday's game against the St. Louis Rams, Jim Zorn said.
"He felt it pop," Zorn said of Thomas's injury. "So we're going to get that repaired. He'll go on injured reserve."
Thomas was at Redskins Park on Monday but did not speak to the media.
Instead, he issued a statement via the team's public relations department.
"I am just very disappointed right now," Thomas said. "It hurts because I want to be out there with my teammates. I worked really hard in the offseason and was looking forward to this year.
"I will have the surgery this week and focus my attention on rehabbing. I will be there every step of the way to help support my teammates the rest of the season. I believe in them and know we can continue to be successful."
Thomas suffered the injury in the second quarter of the Rams game and did not return. He watched the second half from the Redskins' bench with his injured arm wrapped tightly.
It's the second time in three seasons that Thomas has suffered a triceps injury. In 2007, he suffered a torn triceps to his left arm and missed 13 games.
Will Montgomery replaced Thomas in the lineup on Sunday.
Chad Rinehart, Thomas's backup on the depth chart, was inactive for the game.
Thomas is in his 11th NFL season and his seventh in Washington. He has started 144 career games, all at right guard.
The Redskins began the process of to revamping the right side of the offensive line last offseason.
The team released veteran Jon Jansen, who now is a backup with the Detroit Lions, this Sunday's opponent.