"It looks like he has an ACL tear. As of right now, we're proceeding as if he's done for the season," coach John Harbaugh said Monday.
On his Twitter account, Washington wrote: "Thanx for all of your support. Yes I do have a torn ACL. But I'll get through this. Go Ravens."
Washington has started all 10 games in 2009 for the Ravens (5-5). Although the five-year veteran does not have an interception, he's made 40 tackles -- including a career-high tying nine in a win over Denver earlier this month.
With Washington gone, rookie Lardarius Webb should receive more playing time.
"Lardarius is going to be a big part of the plans. Chris Carr is in the mix and Frank Walker is in the mix, and we'll see if we bring somebody else in at corner to kind of bolster us up a little bit," Harbaugh said.
The Ravens have lost five of their last seven games to fall into the middle of the pack in the playoff hunt. If Baltimore is to make a second straight appearance in the AFC championship game, a strong finish is a must.
"It's basically for us a six-game season," Harbaugh said. "As the record stands, we're a 5-5 football team. But we're also a real good football team, a football team that has an opportunity to achieve some very serious goals, really every goal that we had at the beginning of the season."
Baltimore has played well but come up tantalizingly short against several of the best teams in the NFL. The losses include: 27-21 to New England, 33-31 to Minnesota, 17-14 to Cincinnati and, on Sunday, 17-15 against the unbeaten Colts.
"We aspire to be one of the elite teams in the National Football League, and in order to achieve that, those are the games you've got to find a way to win," Harbaugh said. "Not all of them, but you've got to win your share of those games. We've got two of those games coming up in the next two weeks."
Baltimore hosts Pittsburgh on Sunday night before traveling to Green Bay.
"We all understand what needs to happen now. You can't get in the playoffs unless you win 10 games or more," wide receiver Derrick Mason said. "We have to win every game from here on out, point blank. Anyone who doesn't think that we don't have to win all these games, they're lying to themselves."
The Ravens certainly appear capable. Baltimore had 20 first downs and 354 yards in offense against Indianapolis, but couldn't score a touchdown -- not even after getting a first-and-goal at the Indianapolis 1.
"It's just execution," center Matt Birk said. "We're moving the ball in between the 30s. When you get in the red zone, you just have to be that much sharper. We have to find a way to put it in the end zone. There's your duh quote of the week."
The Ravens are 17 points away from being 9-1. Instead, they're at .500.
"We know we're a good football team. I guarantee the people that play us know what kind of a football team we are," Harbaugh said. "The difference is finding a way to win those games against good football teams. That's what you have to do to be an elite football team in this league. I know we're going to be that. It's a matter of when, and we need to make it happen this week."