Lewis tore his right triceps in Sunday's game against Dallas and underwent surgery on Wednesday, a league source told ESPN NFL Insider Ed Werder. Lewis is not planning to travel with the Ravens for their game Sunday against the Texans, the source said.
Although coach John Harbaugh said Monday that the 37-year-old linebacker is out for the year, the Ravens placed Lewis on injured reserve with the "designated to return" tag. By rule, Lewis must sit out eight weeks before he can return this season. He will be eligible to practice after six weeks and permitted to return to play in Week 15 if he's healthy.
However, the timetable to return from a torn triceps, which Harbaugh described as a "full tear" on Monday, is longer. A better estimate on the recovery period from the surgery can be determined depending on whether the tear is to the tendon or the muscle.
Lewis does not count against the 53-man roster.
"We have no idea whether that time frame has anything to do with the injury, but there's an opportunity and we're going to keep the door open," Harbaugh said. "We'll just see where that goes moving forward."
The loss of Lewis coincides with the return of linebacker Terrell Suggs, the 2011 NFL defensive player of the year. Suggs practiced Wednesday for the first time this season after missing months with a torn right Achilles tendon.
Suggs is still favoring his right leg, so the Ravens aren't expecting much from him too soon.
"To what extent, to what he's able to do, I think we should temper our expectations a little bit," Harbaugh said. "He's coming off a very serious injury. I think he's worked really hard. He's done a great job with the rehab, he's followed protocol. He had no setbacks throughout the course of the whole deal."
To fill the void left by Lewis' removal from the roster, the Ravens activated linebacker Josh Bynes from their practice squad.
Lewis leads the Ravens in tackles and is the unquestioned leader not only of the defense but also of the entire team.
Asked who might assume the leadership role, Harbaugh replied, "You replace that with 53 guys. ... Ray is still with us. He'll be around and be a part of what we're doing."
Harbaugh also revealed Wednesday that cornerback Lardarius Webb tore his meniscus as well as his ACL in his left knee in the victory against the Cowboys. Webb was placed on season-ending injured reserve Tuesday and will undergo surgery later this week.
"They'll fix both of those things and we'll let you know how it goes," Harbaugh said, according to the team's website.
Information from The Associated Press was used in this report.