OWINGS MILLS, Md. -- Ravens linebacker Ray Lewis will miss the remainder of the season with an arm injury, an enormous blow to an already depleted defense that has uncharacteristically struggled this year.

Lewis tore his right triceps during Sunday's 31-29 victory over Dallas. Lewis, 37, leads Baltimore in tackles and is the voice of experience in the huddle.

"Ray in the locker room afterward, we didn't know (the extent of the injury), but he was worried about it," Ravens coach John Harbaugh said Monday. "He said some things about his faith. He said some things that I'll never forget."

Over a spectacular 17-year career, Lewis has been invited to 13 Pro Bowls, was named Super Bowl MVP and is a two-time NFL defensive player of the year. He will turn 38 in May, so it's possible that Sunday's game was his last.

"That's for Ray to speak on," Harbaugh said.

Baltimore also lost cornerback Lardarius Webb for the season after he tore the ACL in his left knee Sunday. The injury occurred when Webb collided with Dallas wide receiver Dez Bryant in the first quarter.

Webb was officially placed on injured reserve Tuesday and rookie running back Bobby Rainey was elevated from the practice squad. Rainey, a rookie free agent from Western Kentucky, rushed 23 times for 55 yards in four preseason games with Baltimore. He also had 14 catches for 163 yards and two touchdowns.

Haloti Ngata, the team's best player on the defensive line, also was hurt in the game, tearing his MCL, a league source told ESPN NFL Insider Adam Schefter. Ngata, however, is likely to play Sunday against the Texans despite the injury, the source said.

Sources told ESPN NFL Insider Ed Werder that Lewis informed people immediately after Sunday's game that he unintentionally played two more defensive snaps after suffering the injury. He was not injured while tackling Cowboys running back Phillip Tanner on what proved to be Lewis' final play of the season.

In fact, Lewis was hurt two plays before that, hitting his elbow while making another tackle. He stayed in for another play, realized he was seriously injured and attempted then to leave the field. But the Cowboys came to the line quickly and snapped the ball. Sources said Lewis was hoping they wouldn't run at him because he wanted to avoid further contact before the Ravens medical staff could assess his injury on the sideline. Instead, Tony Romo handed to Tanner, who ran right at Lewis. The linebacker moved to make the play with his left arm to avoid making the injury to his right even worse. Lewis made the tackle with his right arm hanging at his side.

Neither Lewis nor Webb spoke after Sunday's game, and both were unavailable for comment on Monday.

For Harbaugh, it was more about the players than the impact losing them would have on the team.

"I'm disappointed for those guys," Harbaugh said. "It doesn't matter how I or someone else feels about it. It's their thing. These are guys that put so much effort, heart and soul into what they do."

Webb missed the latter part of his rookie season in 2009 with a torn right ACL, and now he's facing surgery again.

"Lardarius was distraught. I could see it when I walked onto the field, on his face," Harbaugh said. "He kind of knew because he's been through it before. I just felt like he knew. He was just beside himself."

The loss of Webb took some of the edge off Baltimore's third straight win.

"I'm hurting for that guy right now," safety Ed Reed said. "I know how hard he works to be out here and what he brings to the game. We have to play for him and pick him up because he's young."