Fox Sports' Jay Glazer (via Steve Layman of NewsChannel 5) first reported the severity of the injury.
Lewan reached three straight Pro Bowls from 2016 to 2018. He earned a four-game suspension for a violation of the NFL's performance-enhancing drug policy, which ruined his chances of making it four straight Pro Bowl trips.
Still, Lewan helped the Titans finish fourth in adjusted line yards, per Football Outsiders.
Despite the offseason departure of Jack Conklin, the offensive line continues to be a strength for Tennessee. The unit is not only ninth in adjusted line yards but also fifth in adjusted sack rate.
Lewan's value to the Titans was evident in the third quarter. Ty Sambrailo, his replacement at left tackle, allowed J.J. Watt to sack Ryan Tannehill and force a fumble.
With Lewan out for the year, Sambrailo probably won't be the answer.
The Denver Broncos traded the Colorado State alumnus to the Atlanta Falcons only two years after selecting him in the second round of the 2015 draft. He has made just 13 starts over five-plus seasons.
Isaiah Wilson will likely be elevated to the first string instead. Wilson has yet to make his NFL debut and was only activated from the reserve/COVID-19 list on Oct. 10.
The Titans grabbed Wilson with the 29th overall pick as part of their long-term solution to replace Conklin. Lewan's injury may force the team to change that plan.