"He's not going to make it back this year," head coach Pete Carroll said Monday while appearing on 710 ESPN Seattle. "Beyond that, it's up to him."
This is another blow for the Seattle secondary that is already without cornerback Richard Sherman for rest of the season after he ruptured his Achilles.
Chancellor missed only one game in his first four seasons in the league after Seattle selected him in the fifth round of the 2010 draft. However, he played 11 games in 2015, 12 games last year and just nine in 2017 before this injury.
The four-time Pro Bowler has been a marquee piece of Seattle's Legion of Boom secondary that helped the team reach two of the last four Super Bowls. He's an enforcer over the middle who dishes out punishing hits to receivers daring enough to venture across the field.
The Seahawks likely will continue to rely on Bradley McDougald at safety alongside Earl Thomas as they battle for playoff positioning in the NFC down the stretch.
Seattle is 7-4 following Sunday's victory over the San Francisco 49ers, placing it a game behind the Los Angeles Rams in the NFC West and tied with the Atlanta Falcons (who beat the Seahawks head-to-head) for the final wild-card spot.
The secondary will be tested without Chancellor in the upcoming contest against Carson Wentz and the 10-1 Philadelphia Eagles with postseason berths hanging in the balance.